Abstracts

Proper Quantification of an Important Phenomenon in Visual Search
Cox, P. H., Adamo, S.H., Porfido, C.L., Kravitz, D.J., & Mitroff, S.R. (2019, November). Proper Quantification of an Important Phenomenon in Visual Search. Poster presented at the annual meeting of the Psychonomic Montreal, QC.

Subsequent search miss (SSM) errors, where observers are prone to miss a second target after finding a first, are well documented in academic radiology and cognitive psychology. Tis phenomenon has critical implications in real word scenarios, such as radiology, where missing a target can be fatal. Cognitive psychologists have sought to study the mechanisms underlying SSM errors with simplified and randomly generated displays, but the most widely used SSM measures have contained a circularity that inflates error estimates (Adamo et al., 2019). Specifically, SSM errors were often defined as the difference between the hit rate for a second target on dual-target trials and the hit rate on single target trials. However, in dual-target displays, the easier target is likely to be found first. Consequently, second-target data are biased to come from a harder distribution compared to single target data. We previously proposed an analysis method using matched displays to remedy this bias. Te current set of studies revisits how a number of factors such as time pressure, trial type proportions, and target-distractor salience manipulations, influence the SSM effect using this unbiased measure.
Psychonomic Society 2019

Using Big Data to Investigate the Short-Term and Long-Term Synaptic Maintenance of Implicit Learning
Kramer, M. R., Cox, P.H., Mitroff, S.R., & Kravitz, D.J. (2019, November). Using Big Data to Investigate the Short-Term and Long-Term Synaptic Maintenance of Implicit Learning. Poster presented at the annual meeting of the Psychonomic Montreal, QC.

Behavior does not occur in isolation; humans constantly accumulate information and adapt their behavior with experience. We recently showed moment-by-moment evidence implicitly accumulates in a manner that considers both the strength and amount of prior evidence (Kramer, Cox, Mitroff & Kravitz, under review). Tis implicit accumulation was long-lasting, surviving across delays and interference. Here, we titrate the effect delay to examine consolidation of the implicit memory over the first 48 hours using a massive behavioral dataset from the mobile application Airport Scanner. Implicit evidence accumulation from a first session predicted behavior at the start of the next session if it occurred within 1 hour or after a delay of 12 hours to 2 days, but it did not predict performance after a delay of 1 to 12 hours. These time windows are consistent with established short-term (Mongillo, Barak & Tsodyks, 2008) and long-term (Kelleher, Govindarajan & Tonegawa, 2004) synaptic weight changes— long-lasting depolarization and long-term potentiation, respectively. Tis pattern of consolidation supports proposals that implicit learning manifests as neural plasticity throughout the cortex (Reber, 2013).
Psychonomic Society 2019

Perils of Using Psychology Subject Pools for Cognitive Psychology Research
Mitroff, S.R., Porfido, C.L., Cox, P.H., Adamo, S.H. (2019, November). Perils of Using Psychology Subject Pools for Cognitive Psychology Research. Talk presented at the annual meeting of the Psychonomic Montreal, QC.

Many cognitive psychology laboratories recruit participants through department-run subject pools, wherein students participate in studies for course credit. Students gain firsthand research experience and researchers gain free access to participants. Critically, students self-select when they participate over the course of an academic term, with some choosing the start and some choosing the end. Previous studies from social psychology have shown that students who choose to participate early in the term score higher on measures of conscientiousness and neuroticism and differ from late participating students on various individual difference metrics. However, there are mixed findings on whether cognitive psychology research is impacted by time of participation. Here, a visual search task was run at the start and end of multiple terms with two early and two late cohorts. Early participants were more accurate at difficult searches, less likely to be outliers, more likely to arrive on time, and less likely to no-show. The findings suggest there are meaningful differences between results from experiments run at the beginning vs. end of a term that can impact both cognitive psychology research and practical aspects of conducting studies.
Psychonomic Society 2019

Recruiting from the shallow end of the pool: Cognitive performance and study compliance differ between participant pool subjects from the start to the end of an academic term
Porfido, C. P., Cox, P. H., Adamo, S. H., & Mitroff, S. R., (2019, November). Recruiting from the shallow end of the pool: Cognitive performance and study compliance differ between participant pool subjects from the start to the end of an academic term. Poster presented at the annual meeting of the Object Perception, Attention, and Memory meeting, Montreal, QC.

Cognitive psychologists often recruit participants through organized subject pools. Such pools offer easy data collection, yet present unforeseen confounds. Social and clinical psychology research has found demographic, personality, and motivational differences between students who participate at the start versus the end of an academic term. However, cognitive psychology research is more equivocal with evidence for and against cognitive differences based on time-of-term participation. Here a visual search task demonstrated differences in accuracy between start- and end-of-term participants, and that end-of-term participants were less reliable (more outliers and no-shows). Research implications will be discussed.
OPAM 2019

Leveraging "big data" to examine the relationship between priming and response inhibition
Nag, S., Mitroff, S. R., & Kravitz, D. J. (2019, November). Leveraging “big data” to examine the relationship between priming and response inhibition. Poster presented at the annual meeting of the Object Perception, Attention, and Memory meeting, Montreal, QC.

Priming and response inhibition have traditionally been considered as two separate phenomena that operate via distinct mechanisms. Recent evidence (e.g., “selection history” effects on behavior, perceptual cortex involvement in high-level cognition) raise the intriguing possibility that priming and response inhibition might actually have an overlapping mechanism. A big data approach was used to compare the magnitude of priming and inhibition effects for a large number of targets in a visual search paradigm. This analysis provides the opportunity to compare and contrast priming and response inhibition in the same paradigm, while examining their relationship across visual stimuli and individuals.
OPAM 2019

Changes in target-distractor similarity space with experience in complex visual search
Cox, P. H., Mitroff, S. R., & Kravitz, D. J. (2019, May). Changes in target-distractor similarity space with experience in complex visual search. Poster presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

Studies of visual search—looking for targets among distractors—typically focus on quantifying the impact of general factors (e.g., number of distractors) on search performance. However, search efficiency, particularly in complex environments, is undoubtedly a function of the particular similarity relationships between the specific target(s) and distractors. Further, the visual system represents many different dimensions (color, location, category) that can be flexibly weighted according to current goals, implying that different similarity relationships may be important in distinct contexts. In the current study we examined the impact of similarity in complex visual search by using “big data” from the mobile app Airport Scanner, where the player serves as an airport security officer searching bags for a diverse set of prohibited items among a large heterogeneous set of potential distractors. This large variability in possible targets and distractors, combined with the volume of data (~3.6 billion trials, ~14.8 million users), provide a means to explore the impact of target-distractor similarity on search. The game also includes levels that players advance through in sequence, enabling an investigation of the effect of experience. The data were used to calculate the impact of every distractor on every target at each level, and the resulting behavioral matrices were then compared to a number of different similarity metrics derived from image statistics (e.g., color, pixelwise) and biologically-inspired models of vision (e.g., HMAX). The analyses revealed that experience shaped the impact of distractors, with lower-level metrics dominant early and higher-level features becoming increasingly important as target and distractor familiarity increased. The detailed understanding of search revealed by these analyses provides key insights for generating a detailed model of real-world search difficulty.
VSS 2019

Accurately quantifying the subsequent search miss effect in multiple-target visual search
Adamo, S., Cox, P. H., Kravitz, D. J., & Mitroff, S. R. (2019, May). Accurately quantifying the subsequent search miss effect in multiple-target visual search. Talk presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

Subsequent search miss (SSM) errors, wherein observers are prone to miss a second target if a first was already detected, are well documented in academic radiology and cognitive psychology. This phenomenon (originally called satisfaction of search) has critical implications as radiologists are more likely to miss an abnormality if a prior abnormality was detected. Cognitive psychologists have replicated the SSM effect with simplified and randomly-generated search displays in attempts to inform its underlying cause(s). Within these experiments, a SSM effect is typically taken as the difference between the hit rate for a second target on dual-target trials and the hit rate on single-target trials. However, this approach may artifactually inflate estimates of SSM errors. In dual-target displays, the easier target is likely to be found first, implying that the second target is more difficult. Consequently, second-target data are more likely to come from the harder portion of the distribution of trials, whereas single-target data include the full range of target difficulty. The current study demonstrates that this participant-driven circularity inflates empirical estimates of the SSM effect, but nowhere near enough to explain the entire effect. Further, the circularity can be avoided with matched single and dual-target displays, so that whichever target is detected second, a matched single-target trial is available for comparison. This “matched-display” design, already widely used in radiology, equates many confounds that make a target harder to find (e.g., clutter). While previous SSM studies in cognitive psychology are still informative, they likely overestimated the absolute SSM effect. This study argues for a course correction to unbiased methods and designs, which will ultimately improve the sensitivity of SSM experiments by removing an artifactual inflation. Moreover, it is important to consider other psychology paradigms that might include similar participant-driven circularities as this issue is not isolated to SSM studies.
VSS 2019

A Big Data Approach to Revealing the Nature of Carryover Effects
Michelle R Kramer, Patrick H Cox, Stephen R Mitroff, Dwight J Kravitz (2019, May). A Big Data Approach to Revealing the Nature of Carryover Effects. Poster presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

Behavior does not occur in isolation—every cognitive act is influenced by prior experiences and can influence behavior that follows. In experimental design, this manifests as a “carryover effect” (i.e., the influence that a trial has on those that follow). Carryover is challenging to study as each trial must be considered individually. Given the power limitations, most studies focus on effects derived from averaging across trials, and randomize and counterbalance trial order to avoid any systematic effect of carryover. However, this does not change the fact that each individual still experiences an effect of carryover, creating a source of noise, particularly for individual difference experiments. Here, we leverage big data to investigate the nature of carryover, showing that performance is drastically influenced by both the absolute number and relative proportion of prior trials that match or do not match the current trial type, even across an interfering task. The optimization of behavior is proportional to the binomial z-test (R2 = 0.950, p = 1.02*10-23) and is domain-general, with the same pattern found across more than one task and dimension. This precise, scale-free mechanism suggests the implicit optimization of behavior likely occurs in local circuits and involves the striatum and/or local synaptic weight changes. Furthermore, using a novel touch-and-swipe response time measure, we can disentangle the influence of trial history on pre-potent motor responses versus actual task-relevant decisions, with each component showing unique and separable effects. The motor response component is speeded with repetition of any condition regardless of whether or not it matches the current trial condition, whereas the decision component follows a linear pattern, with efficiency defined by the degree to which the accumulated evidence is consistent with the current trial condition. These results reveal the striking and systematic mechanisms by which behavior is optimized to the current context.
Acknowledgement: Army Research Office #W911NF-16-1-0274
VSS 2019

Revealing the Nature of Carryover Effects: Using Big Data to Quantify Evidence Accumulation in Behavioral Data
Kramer, M. R., Cox, P. H.,Kravitz, D. J. & Mitroff, S. R. (2018, November). Revealing the Nature of Carryover Effects: Using Big Data to Quantify Evidence Accumulation in Behavioral Data. Poster presented at the annual meeting of the Psychonomic Society, New Orleans, LA.

Every cognitive act (thought, behavior, etc.) is influenced by prior acts and can influence subsequent acts. While apparently tautological, this fact is often ignored in experimental design and analysis. Some fields embrace that prior evidence guides subsequent behavior (e.g., statistical learning and contextual cueing), but most studies are agnostic to such influences, averaging across them. However, these carryover effects are interesting in their own right and understanding them may also yield insights that can be leveraged to improve design and analysis. Here, using a massive dataset of a series of binary decisions from the mobile application Airport Scanner, the effect of prior evidence on current behavior was found to be related to both its consistency and amount. The impact of these metrics on behavior followed a power curve, suggesting humans implicitly evaluate evidence in a way deeply related to
inferential statistics. Moreover, these effects persisted to later testing sessions after an interfering task. These results suggest that implicit learning follows the general form of statistical inference and that accounting for this effect may increase the inferential power of cognitive psychology experiments.
Psychonomic Society 2018

Mapping the behavioral similarity space of targets and distractors in complex visual search
Cox, P. H., Mitroff, S. R., & Kravitz, D. J. (2018, November). Mapping the behavioral similarity space of targets and distractors in complex visual search. Poster presented at the annual Object Perception, Attention, and Memory meeting, New Orleans, LA

Real-world visual searches often involve a wide range of targets amongst a heterogeneous set of distractors. To fully understand the nature of, and influences on, such searches, it is necessary to precisely measure the impact of similarity among a large set of distractors and targets on search performance. Here, we used a massive dataset to quantify the behavioral impact of each of large number of heterogeneous distractors on search for ~100 different targets. This approach provides insights into the effects of target-distractor and distractor-distractor similarity along a number of dimensions (color, category, frequency, etc.) on visual search.
Acknowledgement: Army Research Office

OPAM 2018

The massive impact of carryover effects: Behavior is dramatically and systematically shaped by prior trials
Kramer, M. R., Cox, P. H., Mitroff, S. R., & Kravitz, D. J. (2018, November). The massive impact of carryover effects: Behavior is dramatically and systematically shaped by prior trials. Talk presented at the annual Object Perception, Attention, and Memory meeting, New Orleans, LA

Cognitive psychologists counterbalance/randomize trial order to avoid systematic sequence effects, but this does not remove the noise. Using two massive independent datasets we show that prior experience—specifically, the absolute number and relative proportion of prior trials that match or do not match the current trial type—dramatically influences performance on the current trial, even across an interfering task. Remarkably, this influence manifests as a power curve—the equation underlying t-tests. Thus, the optimization of behavior is proportional to statistical evidence—the impact of which can be anticipated and removed, increasing power to detect real differences between conditions.
Acknowledgement: Army Research Office

OPAM 2018

Escaping isolation: Using “big data” to demonstrate trial-by-trial, and session-by-session, influences on cognition
Kramer, M. R., Kravitz, D. J., & Mitroff, S. R. (2017, November). Escaping isolation: Using “big data” to demonstrate trial-by-trial, and session-by-session, influences on cognition. Poster presented at the annual Object Perception, Attention, and Memory meeting, Vancouver, BC.

Most cognitive psychology experiments rely on the false assumption that trials exist independently (with notable exceptions; e.g., statistical learning). The current study used a massive dataset to investigate carryover effects to show how quickly the cognitive system optimizes itself based on experience. Evidence accumulation was found to occur both locally (within a sequence of trials) and globally (across distinct testing sessions). Individuals rapidly accumulate contextual information in a sophisticated manner that considers both the proportion and absolute number of prior stimulus occurrences, using it to guide behavior. This has implications for our understanding of learning, experimental design, and statistical inference.

Acknowledgement: Army Research Office

OPAM 2017

Mammography to tomosynthesis: Examining the differences between two-dimensional and segmented-three-dimensional visual search
Adamo, S. H., Ericson, J. M., Nah, J. C., Brem, R., & Mitroff, S. R. (2017, November). Mammography to tomosynthesis: Examining the differences between two-dimensional and segmented-three-dimensional visual search. Paper presented at the annual Object Perception, Attention, and Memory meeting, Vancouver, BC.

Breast cancer detection is moving from mammography, examining 2D images, to tomosynthesis, examining segemented-3D images. Tomosynthesis reduces false alarms and improves cancer detection, but takes longer to perform. The added time can be costly, so it is important to understand tomosynthesis to inform how it is employed. To examine segmented-3D search, the current project developed a paradigm that explores differences between 2D and segmented-3D search. Testing with radiologists and undergraduates revealed findings that mimicked radiology performance patterns. This paradigm offers a new tool for examining difference between mammography and tomosynthesis and the mechanisms of segmented-3D search.

OPAM 2017

Perfection and satisfaction: A motivational predictor of cognitive abilities
Onefater, R. A., Kramer, M. R., & Mitroff, S. R. (2017, November). Perfection and satisfaction: A motivational predictor of cognitive abilities. Poster presented at the annual Object Perception, Attention, and Memory meeting, Vancouver, BC.

Individuals’ motivation can influence their cognitive abilities, and an intriguing question is whether different motivational styles align with better or worse cognitive performance. The current study used a large dataset from a mobile game to explore differences between “Perfectionists”—those who strive for errorless performance and “Satisfiers”—those who look to keep progressing, regardless of whether errors were made or not. Perfectionists had better attentional abilities than Satisfiers, evident through more efficient and effective visual search and heightened performance in a separate object sorting task. These results indicate that individual differences in motivation can predict fundamental differences in cognitive performance.

Acknowledgement: Army Research Office

OPAM 2017

What most distracts us?: Using "big data" to understand the effect of target-distractor similarity in visual search
Schubel, L. C., Cox, P. H., Kramer, M. R., Kravitz, D. J., & Mitroff, S. R. (2017, November). What most distracts us?: Using "big data" to understand the effect of target-distractor similarity in visual search. Poster presented at the annual Object Perception, Attention, and Memory meeting, Vancouver, BC.

Visual search is a vital task for a series of professions including airport security screening and radiology. Such searches are complex and targets are often accompanied by a diverse and variable range of distractors. The current project looked at how a near-miss distractor (a distractor that is similar to a particular target) in a search can affect target detection. Specifically, we looked at the effect of near-miss distractors on target accuracy using “big data” from the mobile app Airport Scanner when the target appears to the player for the first time. The presence of a near-miss distractor in the set of possible distractors decreased search performance for the related target, even when the near-miss distractor was not present in the current search trial.

Acknowledgement: Army Research Office

OPAM 2017

Breast cancer detection is undergoing a technological shift—moving from mammography, a process that takes a twodimensional (2D) image of breast tissue, to tomosynthesis, a technique that creates a segmented three-dimensional (3D) image. Tomosynthesis leads to fewer false alarms and more hits, but takes much longer. This added time is a problem as it is not clear how clinical practices can manage more time per patient (while maintaining the same number of patients). This can lead to detrimental effects for the radiologists (e.g., fatigue) and patients (e.g., more errors due to the radiologists’ fatigue). The current study looked to establish a new paradigm that could reliably examine the differences between 2D and segmented- 3D search among both radiologists and undergraduates. The results from both participant groups matched the performance patterns found in previous radiology studies, suggesting that this paradigm could provide a flexible and cost effective tool to better understand tomosynthesis and segmented-3D search more broadly. Subsequent insights can potential improve clinical practice and search theories.

Psychonomic Society 2017

Applied Visual Search: Studying Search in Practical Situations
Mitroff, S. R., Adamo, S. H., & Kramer M. K. (2017, November). Applied Visual Search: Studying Search in Practical Situations. Paper presented at the annual meeting of the Psychonomic Society, Vancouver, BC.

One important goal of cognitive psychology research is to use concepts derived in the lab to guide “real-world” applications. Well-controlled laboratory experiments have yielded fundamental insights into cognitive mechanisms, however generalizing to less-controlled contexts outside the lab remains a critical, yet underexplored arena. Several sub-fields have embraced translational goals, and visual search is one area that has had some success in informing applied practices. This presentation will highlight recent work that has examined visual search in both the lab and “real-world” settings and links the two together quantitatively. We will show how data from a range of participants (students, radiologists, airport security screeners, mobile app players) collectively demonstrate that lab-based findings can inform practical applications. For example, we will discuss recent data showing we can use a simple search task from an app to predict airport security screeners’ actual on-job performance. Likewise, we will discuss a new basic-science paradigm that can potentially be used to inform radiological practices in the clinic. Ultimately, testing cognitive theories in and out of the lab can strengthen the theories and advance society.

Psychonomic Society 2017

Modeling the Visual Search Literature I: An Empirical Estimate of a Priori Power
Kravitz, D. J. & Mitroff, S. R. (2017, November). Modeling the Visual Search Literature I: An Empirical Estimate of a Priori Power. Paper presented at the annual meeting of the Psychonomic Society, Vancouver, BC.

Increasing calls for and evidence suggesting the necessity of publishing null results and pre-registering experiments (e.g., Nosek et al., 2015) heightens the importance of a priori power estimation. Interpreting null results, particularly the absence of an effect, requires confidence in the a priori ability to detect that effect (as does pre-registration). Unfortunately, current estimates of power may not be sufficient, as they are both simplistic and assumption heavy. The current study used a massive visual search dataset (>11 million participants, >3 billion trials; Airport Scanner, Kedlin Co.) to produce empirical estimates of a priori power. Dividing the dataset into numerous independent replications of various designs allows for estimating the minimum effect size each design can reliably (>95%) detect (a priori power). Under these analyses, null results now provide evidence that the effect is no larger than minimum effect size. Similar analyses found false positive rate estimates are particularly high for experiments with few trials but many participants.

Psychonomic Society 2017

Individual differences in susceptibility to irrelevant environmental influences predict visual search performance
Kramer, M. R., Wynn, R. M., Kravitz, D. J., & Mitroff, S. R. (2017, May). Individual differences in susceptibility to irrelevant environmental influences predict visual search performance. Paper presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

Often it is vital to process currently relevant information while resisting task-irrelevant influences. For example, radiologists must focus on their current patient’s images while blocking out the previous patient’s details. It is intriguing to consider that certain individuals are more susceptible to task-irrelevant environmental biases, and how such biases could influence visual search performance. To investigate, data were analyzed from the mobile application Airport Scanner (Kedlin Co., www.airportscannergame.com), a game wherein users assume the role of airport security officers searching simulated x-ray luggage for prohibited items. In a minigame following each level, players were to quickly sort individual items as either prohibited or allowed. Critically, in any given mini-game, prohibited items appeared with a 25%, 50%, or 75% probability. Susceptibility to environmental biases was operationally defined as the magnitude of the accuracy cost in low vs. high probability conditions, with those who were more influenced by the task-irrelevant factor of item probability deemed as those with a larger bias. Individuals who were more susceptible to the probability bias were more influenced by trial-to-trial information in the main visual search task. Specifically, higher probability biases related to (1) lower accuracy during low prevalence searches, (2) higher false alarm rates following an incorrect target miss as compared to a correct target hit, and (3) slower and less accurate target identification following a target present trial than a target absent trial. Importantly, the magnitude of the probability bias did not relate to overall accuracy or target sensitivity, suggesting that the effects were specific to trial-to-trial influences. Collectively, these results suggest individual differences in susceptibility to environmental biases relate to a multitude of search performance metrics and highlight that certain individuals may not be best suited to conduct high-stakes searches (e.g., radiology, airport security).

Acknowledgement: Army Research Office

Vision Sciences Society 2017

Predicting airport screening officers’ visual search competency with a rapid assessment
Mitroff, S. R., Ericson, J. M., & Sharpe, B. (2017, May). Predicting airport screening officers' visual search competency with a rapid assessment. Poster presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

Visual search is a vital cognitive ability for a variety of professions, including airport security, radiology, and the military. Given the importance of such professions, it is necessary maximize performance, and one means to do so is to select individuals based upon their visual search competency. Recent work has suggested that it is possible to quickly classify individuals as strong or weak visual searchers (Ericson, Kravitz, & Mitroff, Psychonomic Society 2016); demonstrating that those who started out faster and more accurate were more likely to have superior performance later in the task. A critical question is whether it is possible to predict search competency within a professional search environment. The current study examined whether a relatively quick visual search task could predict professional searchers’ actual on-job performance. Over 600 professional searchers from the USA Transportation Security Administration (TSA) completed an approximately 10-minute assessment on a tablet-based XRAY simulator (derived from Airport Scanner; Kedlin Co.). The assessment contained 72 trials that were simulated XRAY images of bags. Targets (0 or 1 per trial) were drawn from a set of 20 prohibited items, and distractors (5 to 15 per trial) were taken from a set of 100 allowed items. Participants searched for prohibited items and tapped on them with their finger. Two tutorials had to be successfully complete prior to the assessment. Performance on the assessment significantly related to three on-job measures of performance for the TSA officers: (1) detecting simulated threat items projected into actual carry-on bags, (2) detecting real threat items covertly introduced into the checkpoint, and (3) an annual proficiency exam. These findings suggest that it may be possible to quickly identify potential hires based on their core visual search competency, which could provide organizations the ability to make new hires and assess their current workforce.

Acknowledgement: US Transportation Security Administration

Vision Sciences Society 2017

Estimates of a priori power and false discovery rates induced by posthoc changes from thousands of independent replications
Kravitz, D. J., & Mitroff, S. R. (2017, May). Estimates of a priori power and false discovery rates induced by post-hoc changes from thousands of independent replications. Paper presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

Scientific progress relies on accurate inference about the presence (or absence) of an experimental effect. Failures to replicate high-profile studies have elevated concerns about the integrity of inference in psychology research (Nosek et al., 2015). One proposed solution is preregistering experimental designs before data collection to prevent post-hoc changes that might increase false positives and to increase publication of null findings. However, pre-registration does not always align with the inherently complex and unpredictable nature of research, particularly when a priori power estimates are not sufficient to guide the design of studies. Better a priori power estimates would also increase confidence in interpreting null results. The current study used a massive dataset of visual search performance (>11 million participants, >2.8 billion trials; Airport Scanner, Kedlin Co.; www.airportscannergame.com) to produce empirical estimates of the a priori power of various designs (i.e., number of trials and participants) and to estimate the impact of and appropriate corrections for various posthoc changes (e.g., retaining pilot data). Dividing the dataset into many thousands of independent replications of various designs allowed estimation of the minimum effect size each design can reliably detect (i.e., a priori power). Application of common post-hoc changes to these thousands of replications, yielded precise estimates of the individual and combined impact of post-hoc changes on false positive rates, which in some cases were >30%. Critically, adjusted p-values that correct for post-hoc changes can also be derived. The approach and findings discussed here have the potential to significantly strengthen research practices, guiding the design of studies, encouraging transparent reporting of all results, and providing corrections that allow flexibility without sacrificing integrity.

Vision Sciences Society 2017

Trait anxiety is associated with increased multiple-target visual search errors
Cain, M. S., Dunsmoor, J. E., LaBar, K. S., & Mitroff, S. R. (2017, May). Trait anxiety is associated with increased multiple-target visual search errors. Poster presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

Miss errors are a persistent problem in multiple-target visual searches. In particular, in displays with a mixture of high-salience and harder-to-find low-salience targets, low-salience targets are found less often when they appear with a high-salience target than if they are the only target present. These Subsequent Search Miss (SSM) errors (a.k.a. satisfaction of search errors), are a long-studied problem in radiology and security screening. These searches are both difficult and high stakes: miss errors could lead to fatalities. As such, they present situations where searchers may experience anxiety. SSM errors have been shown to increase when searchers are experiencing anticipatory anxiety (i.e., waiting for a random electrical shock while searching; Cain, Dunsmoor, LaBar, & Mitroff, 2011). Here, in three experiments, we extend these previous findings to show that not only does state-based anticipatory anxiety increase SSM errors, but also that trait-anxious individuals make more SSM errors than searchers with lower self-reported trait anxiety, even with no externally-added anticipatory anxiety. In the first experiment, we selectively recruited individuals who reported either high (N=22) or low (N=18) trait anxiety on the State-Trait Anxiety Inventory (STAI; Spielberger, 1983) in a prescreening questionnaire or previous lab visit. The high-anxiety group had significantly more SSM errors than the low anxiety group (t(35.328)=2.10, p=.043, d=0.67). In a second, preregistered experiment, we recruited 74 participants without pre-screening and had them perform a multiple-target search task, followed by the STAI. SSM error rate and trait anxiety scores were positively correlated (r(72)=.243, p=.037). Finally, in a third experiment with 69 professional airport security searchers, SSM error rate was again positively correlated with trait anxiety scores (r(67)=.251, p=.038). Collectively, these results suggest that both acute anxiety caused by the task and chronic anxiety that the searcher brings with them to the task can make already difficult searches even more error-prone.

Vision Sciences Society 2017

Lingering effects of response inhibition: Evidence for both control settings and memory association mechanisms
Wynn, R. M., Kravitz, D. J., & Mitroff, S. R. (2017, May). Lingering effects of response inhibition: Evidence for both control settings and memory association mechanisms. Poster presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

It is well known that response inhibition (withholding a planned or initiated response) slows subsequent responses, but the exact mechanisms of this effect are not clear. Post-inhibition slowing can have real impacts on performance, so it is important to understand the cause(s). Currently, there are two hypothesized mechanisms: adjustments in general control settings and memory associations made between the inhibition and the stimulus. To examine these possibilities, we tested the time course of inhibition effects on visual search as the two mechanisms predict different patterns; a control adjustment predicts a short-lived, general effect while a memory association predicts a lasting, stimulus-specific effect. Data were obtained from the mobile app Airport Scanner (Kedlin Co., www.airportscannergame.com), a game in which players search simulated x-ray bags for prohibited items. On < 3% of trials, the passenger is an “Air Marshal” and therefore allowed to have a prohibited item, and players must withhold their response. This app offers a massive dataset (currently >2.8 billion trials), providing sufficient data to examine rare inhibition events and their aftereffects as far as 20 trials later. We assessed performance on search trials following either an Air Marshal trial (i.e., inhibition anchor) or a search trial (i.e., search anchor). To differentiate between control setting and memory association accounts of inhibition, we compared stimulus switches, wherein the inhibition anchor and the trial of interest (lags 1-20) had different targets, and stimulus repetitions, wherein the inhibition anchor and the trial of interest had the same target. A brief negative effect was of inhibition on performance was observed during stimulus switches, consistent with adjustments in control settings. A prolonged negative effect was observed during stimulus repetitions, consistent with a memory association account. The results suggest that both memory associations and control settings influence behavior following response inhibition, but on distinct time scales.

Acknowledgement: Army Research Office

Vision Sciences Society 2017

Repetition Priming Preferentially Benefits Infrequent Targets
Scotti, P., Adamo S. H., Mitroff, S. R., & Shomstein, S. (2017, May). Repetition priming preferentially benefits infrequent targets. Poster presented at the annual meeting of the Visual Sciences Society, St. Pete's Beach, FL.

The process of searching for targets among distractors (i.e., visual search) is affected by a wide array of factors. One known factor is that search performance is improved if a previous search trial contained the same target as the current trial, a phenomenon referred to as repetition priming. Repetition priming has been observed in both pop-out search (e.g., Maljkovic & Nakayama, 1994) and conjunctive search (e.g., Becker, 2008; Kristjánsson & Driver, 2008), yet, much remains unknown about the robustness of this phenomenon. For example, previous instantiations of repetition priming have primarily used small sets of possible targets and distractors. The current investigation used a large array of possible targets and distractors in a complex search environment to test the limits of repetition priming and to explore novel factors that might affect it. Data were drawn from the mobile technology app Airport Scanner (Kedlin Co., www.airportscannergame. com), a game wherein players search for prohibited items in simulated images of XRAY baggage. This is an ideal dataset for the current purposes given there are billions of individual trials, millions of unique users, and hundreds of distinct target types. The current study examined whether (1) repetition priming persists across many different targets that range in color, size, and shape; and (2) if individual target frequency (i.e., how often a specific target appears in search) modulates the priming effect. Repetition priming was observed; a target was detected faster if the previous search display contained the same target as opposed to a different target. Target frequency modulated this effect, whereby rarer targets benefitted more from repetition priming. These results suggest that repetition priming has direct consequences for complex searches, such as baggage screening, and that repeated exposure to specific targets attenuates this effect.

Acknowledgement: NSF BCS-1534823 to S. Shomstein

Vision Sciences Society 2017

Visual Search: You Are Who You Are (+ a Learning Curve)
Ericson, J. M., Kravitz, D. J., & Mitroff, S. R. (2016, November). Visual search: You are who you are (+ A learning curve). Poster presented at the annual meeting of the Psychonomic Society, Boston, MA.

The ability to take information learned from one visual search and apply that knowledge to subsequent searches, dubbed “Long-Term Visual Search” (LTVS), provides an important window into how search competencies develop. This project investigated individual differences in visual search performance by examining LTVS in approximately 110,000 participants (data obtained from Airport Scanner, Kedlin Co.; see Mitroff et al., 2015). While all participants demonstrated learning curves, participants largely stayed within a clearly distinguishable zone of performance from their first searches until the end. Those who ultimately became top performers started stronger, while those who ended as bottom performers began weaker. When broken into four distinct groups by their final performance, an individual’s performance in early trials was predictive of their eventual proficiency with over 90% accuracy between top and bottom groups, and over 60% between all pairings, suggesting that searchers’ initial abilities explained a fair proportion of their peak potential.

Psychonomic Society 2016

Modeling the Visual Search Literature II: Correcting for Post- Hoc Design Changes
Mitroff, S. R., Ericson, J. M., & Kravitz, D. J. (2016, November). Modeling the visual search literature II: Correcting for post-hoc design changes. Paper presented at the annual meeting of the Psychonomic Society, Boston, MA.

Scientific progress relies on accurate inference about the presence (or absence) of an experimental effect. Failures to replicate high-profile studies (Nosek et al., 2015) have elevated concerns about the integrity of inference in psychology research. One proposed solution is pre-registering experimental designs before data collection, preventing post-hoc changes that might increase false positives. However, pre-registration does not always align with the inherently complex and unpredictable nature of research. To bolster and add flexibility to the pre-registration process, the current study accessed a massive visual search dataset (>9 million participants, >2.5 billion trials: Airport Scanner, Kedlin Co.) to “run” 100,000+ independent experiments to which common post-hoc changes (e.g., adding participants) were applied. Analyses yielded precise estimates of the individual and combined impact of post-hoc changes on false positive rates, which in some cases were >30%. Critically, adjusted p-values that correct for post-hoc changes can be derived, providing flexibility without sacrificing integrity.

Psychonomic Society 2016

Lasting Inhibition: Mapping the Time Course of Response Inhibition With Big Data
Wynn, R. M., & Mitroff, S. R. (2016, November). Lasting Inhibition: Mapping the time course of response inhibition with bag data. Poster presented at the annual meeting of the Psychonomic Society, Boston, MA.

Response inhibition - withholding a planned action - negatively influences behavior on subsequent trials making performance slower and less accurate. To examine the mechanisms of this inhibition effect, the current study used “big data” from the mobile app Airport Scanner to evaluate time course questions. A prolonged negative effect on performance was observed during stimulus repetitions (inhibited item and later target were identical), consistent with a memory association account. A brief negative effect was observed during stimulus switches, consistent with adjustments in control settings. The results suggest memory associations and control settings influence behavior following response inhibition, but on different time scales.

OPAM 2016

Long-Term Visual Search: Using Mobile-App "Big Data" to Reveal Key Aspects of Experience in Visual Search
Ericson, J. M., Mitroff, S. R., & Sharpe, B. (2016, September). Visual search: Using mobile app "big data" to reveal key aspects of experience in visual search. Paper presented at the annual meeting of the Human Factors and Ergonomics Society, Washington, D.C.

Most professional visual searchers (e.g., radiologists, baggage screeners) face an interesting conundrum—they must be highly accurate while also performing in a timely fashion. Airport security personnel, for example, are tasked with preventing any and all dangerous items from getting aboard a plane, but they must also be speedy to keep the passengers flowing through the checkpoint. It is not easy to simultaneously prioritize two primary job requirements (accuracy and speed) that are in direct contrast to one another. While a certain level of error is inevitable in almost any cognitive task, it is arguable that many professional search environments might be even more vulnerable to error given the contradictory goals imposed upon the searchers. As such, it is critical to explore every means possible to minimize mistakes.

Human Factors and Ergonomics Society 2016

The Long and Short of Visual Search: Examining Both Long- and Short-Term Influences on Search Performance
Mitroff, S. R., Winkle, J., Ericson, J. M., & Gancayco, C. A. (2015, November). The long and short of visual search: Examining both long- and short-term influences on search performance. Paper presented at the annual meeting of the Psychonomic Society, Chicago, IL.

Rough data collected from novice searchers (university participants), professional searchers (TSA officers), and via big data obtained from mobile technology (Airport Scanner; Kedlin; Mitroff et al., 2015), our lab has recently found both short-term and long-term influences on visual search performance. Given the applied nature of search, it is important to understand all influences on performance, regardless of whether the influences are short- or long-lived. From a short-term perspective, we have found trial-by-trial effects such that accurate trials are more likely to follow other accurate trials (i.e., success begets success). From a long-term perspective, we have examined the phenomenon of long-term visual search — the evolution of learning in a new search environment — revealing constant influences on search accuracy and response times, as well as individual difference effects. These data collectively highlight the multifaceted nature of search, and we will discuss the effects individually and in relation to one another.

Psychonomic Society 2015

Moving at the Speed of Search: Long-Term Visual Search and the Influence of Lapses in Time Between Search Activity
Ericson, J. M., Winkle, J., & Mitroff, S. R., (2015, November). Moving at the speed of search: Long-term visual search and the influence of lapses in time between search activity. Poster presented at the annual meeting of the Psychonomic Society, Chicago, IL.

Professional searchers (e.g., airport security personnel, radiologists) often search for targets that rarely appear (e.g., bags seldom contain explosives). Given such infrequency, an important question arises— is search performance affected by the amount of time that passes between occurrences of a particular target type? Does a searcher become less effective at detecting a particular target type if it has been minutes, days, weeks or months since that specific target was last detected? Moreover, natural breaks (lunch, days off, vacation) introduce delays between any search activity, and it vital to understand how such breaks affect performance. Timing-related effects are di cult to address in the lab, but can be examined in the “big data” environment afforded by the mobile application Airport Scanner (Kedlin; Mitroff et al., 2015). We will discuss data from 500,000 participants, which revealed several time-related effects, including that more proficient searchers have smaller time lapses between searches.

Psychonomic Society 2015

Satisfaction at last: Evidence for the “satisfaction” hypothesis for multiple-target search errors
Adamo, S. H., Cain, M. S., & Mitroff, S. R. (2015, November). Satisfaction at last: Evidence for the “satisfaction” hypothesis for multiple-target search errors. Paper presented at the annual Object Perception, Attention, and Memory meeting, Chicago, IL.

Multiple-target visual searches are susceptible to Subsequent Search Miss (SSM) errors—a reduced accuracy for target detection after a previous target has already been detected. SSM errors occur in critical searches (e.g., evaluations of radiographs and airport luggage x-rays), and have proven to be a stubborn problem. A few SSM theories have been offered, and here we investigate the “satisfaction” account: failing to completely finish a search after having found a first target. Accuracy on a multiple-target search task was compared to both how long participants spent searching after finding a first target and their target sensitivity in a separate vigilance task. Less time spent searching and poor vigilance predicted higher SSM error rates. These results suggest that observers who are more likely to miss a second target are less likely to thoroughly search after finding a first target, thus offering some of the first evidence for the “satisfaction” account.

OPAM 2015

Using mobile technology (and big data) to understand medical errors
Mitroff, S. R., Biggs, A. T., Ericson, J. M., Winkle, J., Gancayco, C. A., Adamo, S. H., & Wu Dowd, E. (2015, September). Using mobile technology (and big data) to understand medical errors. Paper presented at the Diagnostic Error in Medicine 8th International Conference, Washington, D.C.

Background: Academic radiology and cognitive psychology research have helped reveal the underlying causes of certain types of medical image search errors; however, several sources of these errors have remained elusive. In the current presentation, we will discuss how data collected from millions of searchers across billions of trials can inform specific medical image search problems that have been especially hard to address in laboratory or clinical settings. Specifically, we will present data that informs search errors related to satisfaction of search—an increased risk of missing a target (e.g., an abnormality in an X-ray) after having already found another target. Methods: We have partnered with Kedlin Co., the makers of a smartphone app called Airport Scanner, to obtain “big data.” Airport Scanner is a game where the player serves as an airport security officer and searches for contraband in simulated carry-on bags. The game contains numerous elements that are ideal for research endeavors—a variable number of targets per bag, a variable number of distractors per bag, multiple levels with varying difficulty, hundreds of different target types and distractor types, a secondary distraction task, etc. We have access to over 2 billion trials from over 7 million devices, and we have used this unique dataset to address questions that have been previously intractable. Results: Multiple-target visual search errors contribute to diagnostic errors related to X-ray image reading, cytology, pathology, etc., and it is critical to understand the core causes of the problem to improve medical image searches and diagnostic performance. We will present a number of findings, include data that suggest that satisfaction of search is partially caused via a ‘perceptual set’ mechanism—after finding a target, you are more likely to find other targets that are perceptually and conceptually similar. Likewise, we will show how target frequency (how often a specific target appears across all searches) can greatly affect diagnostic performance. Conclusions: It is vital to minimize medical image search errors, but this can only be done by understanding the causes of each error type. We will present a novel technique for investigating the general search behaviors that can underlie search errors. This approach complements and expands current research endeavors, and most importantly, can address previously intractable problems.

Diagnostic Error in Medicine International Conference 2015

Using mobile technology (and big data) to inform radiological research
Mitroff, S. R., Biggs, A. T., Ericson, J. M., Winkle, J., Adamo, S. H., & Wu Dowd, E. (2015, June). Using mobile technology (and big data) to inform radiological research. Paper presented at the annual meeting of the Medical Imaging Perception Society, Ghent, Belgium.

Rationale: Academic radiology and cognitive psychology research have helped reveal the underlying causes of certain types of radiological search errors; however, several sources of these errors have remained elusive. In the current presentation, we will discuss how data collected from millions of searchers across billions of trials can inform specific radiological search problems that have been especially hard to address in laboratory or clinical settings. Specifically, we will present data that informs search errors related to satisfaction of search and rarely-appearing targets.
Methods: We have partnered with Kedlin Co., the makers of a smartphone app called Airport Scanner, to obtain “big data.” Airport Scanner is a game where the player serves as an airport security officer and searches for contraband in simulated carry-on bags. The game contains numerous elements that are ideal for research endeavors - a variable number of targets per bag, a variable number of distractors per bag, multiple levels with varying difficulty, hundreds of different target types and distractor types, a secondary distraction task, etc. We have access to over 2 billion trials from over 7 million devices, and we have used this unique dataset to address questions that have been previously intractable [1-4].
Results: We will discuss several findings relevant to radiological search. For example, we have demonstrated that satisfaction of search (an increased risk of missing a target after having already found another target) is partially caused via a ‘perceptual set’ mechanism - after finding a target, you are more likely to find other targets that are perceptually and conceptually similar [1]. Likewise, we will show how target frequency (how often a specific target appears across all searches) can greatly affect search accuracy [3].
Conclusions: It is vital to minimize radiological search errors, but this can only be done by understanding the causes of each error type. We will present a novel technique for investigating the general search behaviors that can underlie radiological search errors. This approach complements and expands current research endeavors, and most importantly, can address previously intractable problems.

References:
[1] Biggs, A. T., Adamo, S. H., Dowd, E. W., & Mitroff, S. R. (in press). Examining perceptual and conceptual set biases in multiple-target visual search. Attention, Perception, & Psychophysics.
[2] Biggs, A. T., Adamo, S. H., & Mitroff, S. R. (2014). Rare, but obviously there: Effects of target frequency and salience on visual search accuracy. Acta Psychologica, 152, 158-165.
[3] Mitroff, S. R., & Biggs, A. T. (2014). The Ultra-Rare-Item effect: Visual search for exceedingly rare items is highly susceptible to error. Psychological Science, 25(1), 284-289.
[4] Mitroff, S. R., Biggs, A. T., Adamo, S. H., Dowd, E. W., Winkle, J., & Clark, K. (2014). What can 1 billion trials tell us about visual search? Journal of Experimental Psychology: Human Perception & Performance.

Medical Imaging Perception Society 2015

Long-term visual search: Examining trial-by-trial learning over extended visual search experiences
Ericson, J. M., Biggs, A. T., Winkle, J. A., Gancayco, C. A., & Mitroff, S. R. (2015, May). Long-term visual search: Examining trial-by-trial learning over extended visual search experiences. Talk presented at the annual meeting of the Vision Sciences Society, St. Pete Beach, FL.

Airport security personnel search for a large number of prohibited items that vary in size, shape, color, category-membership, and more. This highly varied search set creates challenges for search accuracy, including how searchers are trained in identifying a myriad of potential targets. This challenge has both practical and theoretical implications (i.e., determining how best to obtain high accuracy, and how large memory sets interact with visual search performance, respectively). Recent research on “hybrid visual and memory search” (e.g., Wolfe, 2012) has begun to address such issues, but many questions remain. The current study addressed a difficult problem for traditional laboratory-based research—how does trial-by- trial learning develop over time for a large number of target types? This issue, which we call “long-term visual search,” is key for understanding how reoccurring information in retained in memory so that it can aid future searches. Through the use of “big data” from the mobile application Airport Scanner (Kedlin Co.), it is possible to address such previously intractable questions. Airport Scanner is a game where players serve as an airport security officers looking for prohibited items in simulated bags. The game has over 7 million downloads and provides a powerful tool for psychological research (Mitroff et al., 2014 JEP:HPP). Trial-by-trial learning for multiple different targets was addressed by analyzing data from 50,000 participants. Distinct learning curves for each specific target revealed that accuracy rises asymptotically across trials without deteriorating to initially low starting levels. Additionally, an investigation into the number of to-be- searched-for target items indicated that performance accuracy remained high even as the memorized set size increased. The results suggest that items stored in memory generate their own item-specific template that is reinforced from repeated exposures. These findings offer insight into how novices develop into experts at target detection over the course of training.

Vision Sciences Society 2015

An individual differences approach to multiple-target search errors: Errors correlate with attentional deficits
Adamo, S. H., Cain, M. S., & Mitroff, S. R. (2015, May). An individual differences approach to multiple-target search errors: Errors correlate with attentional deficits. Poster presented at the annual meeting of the Vision Sciences Society, St. Pete Beach, FL.

A persistent problem in visual search is that searchers are more likely to miss a target if they have already found another in the same display. This phenomenon, the Subsequent Search Miss (SSM) effect, has remained despite being a known issue for decades. Increasingly, evidence supports a resource depletion account of SSM errors-a previously detected target consumes attentional resources leaving fewer resources available for the processing of a second target. However, "attention" is broadly defined and is composed of many different characteristics, leaving considerable uncertainty about how attention affects second-target detection. The goal of the current study was to identify which attentional characteristics (i.e., selection, limited capacity, modulation, and vigilance) related to second-target misses. The current study compared second-target misses to an attentional blink task and a vigilance task, which both have established measures that were used to operationally define each of four attentional characteristics. Second-target misses in the multiple-target search were correlated with (1) a measure of the time it took for the second target to recovery from the blink in the attentional blink task (i.e., modulation), and (2) target sensitivity (d') in the vigilance task (i.e., vigilance). Participants with longer recovery and poorer vigilance had more second-target misses in the multiple-target visual search task. The results add further support to a resource depletion account of SSM errors and highlight that worse modulation and poor vigilance reflect a deficit in attentional resources that can account for SSM errors.

Vision Sciences Society 2015

For better or worse: Prior trial accuracy affects current trial accuracy in visual search
Winkle, J. A., Biggs, A. T., Ericson, J. M., & Mitroff, S. R. (2015, May). For better or worse: Prior trial accuracy affects current trial performance in visual search. Poster presented at the annual meeting of the Vision Sciences Society, St. Pete Beach, FL.

Life is not a series of independent events, but rather, each event is influenced by what just happened and what might happen next. However, many research studies treat any given trial as an independent and isolated event. Some research fields explicitly test trial-to-trial influences (e.g., repetition priming, task switching), but many, including visual search, largely ignore potential inter-trial effects. While trial-order effects could wash out with random presentation orders, this does not diminish their potential impact (e.g., would you want your radiologist to be negatively affected by his/her prior success in screening for cancer?). To examine biases related to prior trial performance, data were analyzed from airport security officers and Duke University participants who had completed a visual search task. Participants searched for a target “T” amongst “pseudo-L” distractors with 50% of trials containing a target. Four set sizes were used (8,16,24,32), and participants completed the search task without feedback. Inter-trial analyses revealed that accuracy for the current trial was related to the outcome of the previous trial, with trials following successful searches being approximately 10% more accurate than trials following failed searches. Pairs of target-absent or target-present trials predominantly drove this effect; specifically, accuracy on target-present trials was contingent on a previous hit or miss (i.e., other target-present trials), while accuracy on target-absent trials was contingent on a previous correct rejection or false alarm (i.e., other target-absent trials). Inter-trial effects arose in both population samples and were not driven by individual differences, as assessed by mixed-effects linear modeling. These results have both theoretical and practical implications. Theoretically, it is worth considering how to control for inter-trial variance in statistical models of behavior. Practically, characterizing the conditions that modulate inter-trial effects might help professionals searchers perform more accurately, which can have life-saving consequences.

Vision Sciences Society 2015

What Can 1,000,000,000 Trials Tell Us About Visual Search?
Mitroff, S. R., Biggs, A. T., Adamo, S. H., Dowd, E. W., Winkle, J. & Clark, K. (2014, November). What can 1,000,000,000 trials tell us about visual search? Paper presented at the annual meeting of the Psychonomic Society, Long Beach, CA.

In 1998, Jeremy Wolfe collated data from 2500 experimental sessions and 1 million trials to provide key insights into visual search (Wolfe, 1998). This is an example of using big data to reveal new effects and to test theories in a way that is beyond the scope of typical datasets. Through the mobile app Airport Scanner (www.airportscannergame.com), we have amassed visual search data from 70 million experimental sessions and nearly 2 billion trials (so far). In Airport Scanner, players act as baggage screeners and search for illegal items amongst legal distractors. The game interface offers a smorgasbord of variables for vision scientists: hundreds of different targets and distractors, variable numbers of items in each bag, go/ no-go trials, etc. With access to output that includes response time and accuracy data along with descriptive information (type of bag, which targets/distractors were present, etc.), we can ask and answer a wide variety of questions that would be near impossible to address in a standard laboratory setting. In this presentation, we will discuss several research topics we have examined to date. We will also discuss how this, and other forms of big data, can be used to advance psychological science.

Psychonomic Society 2014

 Perceptual and Conceptual Set Biases in Multiple-Target Visual Search
ABiggs, A. T., Adamo, S. H., Dowd, E. W., & Mitroff, S. R. (2014, November). Perceptual and conceptual set biases in multiple-target visual search. Poster presented at the annual meeting of the Psychonomic Society, Long Beach, CA.

Visual searchers, such as radiologists and airport security officers, are more likely to miss additional targets after locating a first target within the search array. Such errors can be serious (i.e., what if a security officer finds a water bottle, but not a gun?), and previous work has shown that multiple-target search errors have numerous contributing causes. One often espoused, but not empirically supported, hypothesis is that searchers become biased to find subsequent targets similar to the first found target (and are therefore less likely to find dissimilar targets). Utilizing “big data” obtained from the mobile application Airport Scanner, the current study tested this hypothesis. Multiple-target search errors were substantially reduced when two targets were identical, suggesting that the first found target did indeed bias subsequent search. Further analyses revealed both a perceptual set bias (i.e., a bias to find additional targets with similar features to the first target) and a conceptual set bias (i.e., a bias to find additional targets with a conceptual relationship to the first target). These findings are discussed in terms of the relationship between attention and working memory in visual search.

Psychonomic Society 2014

The neural cascade of processing underlying response time variability in visual search
Berg, B. V., Appelbaum, L. G., Clark, K., Mitroff, S. R., & Woldorff, M. G. (2014, November). The neural cascade of processing underlying response time variability in visual search. Poster to be presented at the annual meeting of the Society for Neuroscience, Washington, D.C.

Visual search, the process of finding target items among distracters, is a critical cognitive function that is at the core of numerous daily and professional activities. While it is important to be able to rapidly detect targets, there is substantial trial-to-trial variability in this ability. Here we explored the neural mechanisms that may underlie this variability by comparing reaction times (RTs) and various electrophysiological markers as 17 participants performed a popout visual search task. In this task, participants were presented (50 ms duration) with search arrays that each contained a lateralized green popout target and, in the opposite hemi field, a red popout nontarget, among a field of 46 blue distracters. The participants’ task was to orient their attention to the green target ellipse and indicate whether it was “vertical” or “horizontal” with either a left- or right-hand button response. We subsequently extracted from the electrical recordings the event-related potential (ERP) components that index attentional orienting to a target item (the N2pc) and that index motor response initiation (the lateralized readiness potential [LRP]). In addition, neural oscillatory activity was extracted for time intervals both before and after the stimulus occurrence, which was then related to the stimulus-locked ERP markers and behavioral RTs to describe the neural cascade that precedes faster or slower neural processing and RTs. Results demonstrated that the attentional-orienting-related N2pc was significantly earlier for trials with fast RTs compared to slow ones, and this was followed by earlier response preparation, as indexed by earlier motor-related LRPs. Faster RTs were also associated with post-stimulus decreases in fronto-central oscillatory theta activity (4-7 Hz) and increases in beta oscillations (15-25 Hz), indicating both markers reflect processes that ramify to cognitive task performance. Although bilateral prestimulus alpha levels (8-12 Hz) did not covary with RT, lower alpha contralateral to the target side (which is typically associated with more focused spatial attention) predicted larger N2pc amplitudes to those targets, suggesting that greater prestimulus neural engagement to that side resulted in more robust attentional orienting. Contralateral prestimulus alpha did not, however, manifest in faster RTs, suggesting that such variations do not necessarily ramify into faster RTs, at least for these highly salient popout stimuli. Collectively, the results delineate the cascade of neural processes before and after a stimulus array that do and do not lead to response-time variability in pop-out visual search.

Society for Neuroscience 2014

Mapping the Core Factors of Visual Perceptual Performance
Appelbaum, L. G., Bel-Bahar, T., Wang, L., Krasich, K., Hughes, L., Mitroff, S. R. (2013, November). Mapping the core factors of visual perceptual performance. Poster presented at the annual meeting of the Psychonomic Society, Toronto, ON, Canada.

Vision is the building block of much of human cognition. In the present research we describe core performance factors that capture visual cognitive abilities across a wide range of perceptual (static and dynamic visual acuity, contrast sensitivity, depth perception), visual-motor (eye hand coordination, go/no-go, reaction times), and working memory tasks, collected in a sample of 160 healthy college-aged individuals. Measured behavior on each task adhered to typically reported performance for similar types of tasks, and produced largely normal distributions. Across these tasks we observed 4 latent factors that describe variability in performance. These factors are interpreted as reflecting; visual-motor control, perceptual sensitivity, visual quickness, and visual-spatial working memory abilities. We observed an effect of gender on the visual-motor control factor, but not the other factors, with males performing better. Our data suggest that response speed and perceptual sensitivity are separable facets of performance, even when measured within the same task. These findings indicate an initial principled set of visual performance metrics that can be used to explore individual variability relating human visual cognition.

Psychonomic Society 2013

Visuomotor Performance is Predicted by Event-Related Potentials (ERP) in a Rapid Serial Visual Presentation (RSVP) Protocol
Bel-Bahar, T., Gentzler, E., Adamo, S. H., Wang, L., Krasich, K., Hughes, L., Mitroff, S. R., & Appelbaum, L. G. (2013, November). Visuomotor performance is predicted by ERP amplitudes in a rapid serial visual presentation (RSVP) protocol. Poster presented at the annual meeting of the Psychonomic Society, Toronto, ON, Canada.

We report results from an ongoing study examining brains circuits related to visual cognition via ERP and visuomotor performance metrics. ERP data was collected during an attentional-blink RSVP task wherein on each trial 18 numbers and one (T1) or two (T2) target letters were shown serially for 100 ms each (with 100, 300, 400, and 700 ms. “T2-lags”). Performance metrics were computed from a standardized battery that included visual sensitivity and visuomotor tasks. Examining only ERP trials where T1 and T2 were correctly detected, we observed T2-detection accuracy was predicted by P300 amplitude at occipito-parietal channels. ERPs also predicted better visuomotor performance, including scores on reaction time, go-no go, and near-far visual accuracy. These results suggest that occipito-parietal activation may index efficient visual processing and responding. Our findings extend the existing literature on ERP and visual cognition, providing a platform to explore how brain circuits may mediate visuomotor performance.

Psychonomic Society 2013

Finding a Needle (and a Thread, and a Thimble, and…) in a Haystack: Multiple-Target Visual Search for Ultra-Rare Items
Biggs, A. T., & Mitroff, S. R. (2013, November). Finding a needle (and a thread, and a thimble, and…) in a haystack: Multiple-target visual search for ultra-rare items. Poster presented at the annual meeting of the Psychonomic Society, Toronto, ON, Canada.

Many search tasks, including those conducted by professionals in radiology and airport security screening, can contain multiple targets in a single search display. Previous work has repeatedly demonstrated that finding one target can impair accuracy for additional targets present in the same display; however, it remains unclear why this effect, termed “satisfaction of search,” occurs. It is vital to understand the underlying causes to best alleviate multiple-target search errors, yet it is difficult to assess potential influences due to practical limitations. Whether testing in a laboratory-based or real-world setting, it is hard to amass sufficient data to truly tease apart different theories. By using “big data” obtained from the smartphone application Airport Scanner, we were able to compare performance from thousands of players and millions of trials on a multiple-target search task. This large data set, which contains 79 unique target types (60 with prevalence rates below 1%), allowed us to examine how multiple-target search was affected by a variety of factors including item prevalence, perceptual set biases, and visual salience. We will describe how these factors interact to affect multiple-target search accuracy.

Psychonomic Society 2013

Cognitive, Personality, and Neuroimaging Correlates of Media Multitasking
Cain, M. S., Finn, A. S., Gabrieli, J. D., & Mitroff, S. R. (2013, November). Cognitive, personality, and neuroimaging correlates of media multitasking. Paper presented at the annual meeting of the Psychonomic Society, Toronto, ON, Canada.

A growing proportion of media is consumed simultaneously with other media (e.g., reading e-mail while watching television), a behavior known as media multitasking. While the overall rate of media multitasking has been increasing over at least the last decade (Rideout, Foehr, & Roberts, 2010), there remain broad individual differences. We examined the relationship between self-reported media multitasking behavior and a variety of cognitive laboratory tasks (e.g., N-back, Stop Signal), personality and clinical measures (e.g., Big 5, ADHD symptoms), and structural and functional neuroimaging (e.g., cortical thickness, resting-state connectivity) in samples of middle-school students, university undergraduates, and working adults. Collectively, the data suggest that differences in media multitasking behavior may be diagnostic of pervasive differences in attentional and cognitive control, with greater media multitasking behavior correlated with less selective control of attention (i.e., a broader attentional set).

Psychonomic Society 2013

Visual searches need their own personal space: The importance of spacing between simultaneously presented search arrays
Adamo, S. H., Biggs, A. T., & Mitroff, S. R. (2013, May). Visual searches need their own personal space: The importance of spacing between simultaneously presented search arrays. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

Visual search, the process of looking for targets amongst distractors, is an everyday activity executed in a variety of contexts. While searches are often mundane (e.g., looking for your keys) they can also be highly important (e.g., airport baggage screeners looking for contraband). Considerable research has examined the nature of visual search accuracy, but how well do the results generalize to real-world visual searches? For example, most cognitive psychology experiments present observers with a single search array and assess how quickly and accurately target(s) are found. However, airport baggage screeners often view displays that contain multiple search arrays (i.e., several bags on the same x-ray monitor), and these search arrays can be close together and/or appear physically connected (e.g., when passengers shove their bags into the x-ray machine). Here we investigated how accuracy is affected when multiple search arrays are simultaneously present, and whether spacing between arrays impacts performance. Experiment 1 presented 3 search arrays, either spaced close together (5-pixel separation) or far apart (100-pixel separation), and each array could contain 0, 1, or 2 targets. Trials progressed by having the arrays physically shift to the edge of the monitor as if on a conveyor belt, and participants were to only search the center array before advancing. Array spacing did not impact response time or accuracy on single- and no-target trials, but did affect dual-target trials: second target accuracy (after having found a first target in the same array) was significantly worse when the arrays were close together than far apart. Experiment 2 compared trials with 3 far-spaced arrays to trials with only a single array, and there were no response time or accuracy differences. Collectively, the results suggest that search array spacing can negatively impact accuracy for dual-target search, which is a particularly complex search process.

Vision Sciences Society 2013

Visual plasticity: Altering cognition through stroboscopic training
Appelbaum, L. G., Cain, M. S., Schroeder, J. E., Darling, E. F., & Mitroff, S. R. (2013, May).Visual plasticity: Altering cognition through stroboscopic training. Paper presented at the annual meeting of the Vision Sciences Society, Naples, FL.

If people are forced to operate in an impoverished visual environment, might their visual abilities improve once they return to a normal environment? In a set of four experiments we tested this question by determining whether athletic training under stroboscopic visual conditions has the capacity to improve visual perception and cognition. In each experiment, participants were assigned to either an experimental condition wherein they trained with stroboscopic eyewear or to a control condition in which they underwent identical training with non-stroboscopic eyewear. The training consisted of multiple sessions over a number of days during which participants performed athletic drills such as throwing and catching. To determine if training led to generalizable benefits, we used computerized measures to assess perceptual and cognitive abilities on a variety of tasks before and after training. Computer-based assessments included measures of visual sensitivity (central and peripheral motion coherence thresholds), transient spatial attention (a useful field of view – dual task paradigm), sustained attention (multiple-object tracking), and visual memory (partial report task). In all tasks re-test performance was measured immediately after training, and for a subset of the tasks additional participants were re-tested with a 24-hour delay after training to assess retention. Results revealed that stroboscopic training led to significantly greater re-test improvement compared to the control group in central visual field motion sensitivity and transient attention abilities. In addition, stroboscopic training led to enhancements in short-term visual memory capacity, and these trained improvements were maintained for at least 24-hours. No significant training benefits were observed for peripheral motion sensitivity or peripheral transient attention abilities, nor were benefits seen for sustained attention during multiple-object tracking. These findings demonstrate that stroboscopic training can effectively improve some, but not all, aspects of visual cognition and suggest a potentially powerful tool for performance enhancement and/or remediation.

Vision Sciences Society 2013

The effects of searching for something you love (or hate): Duke and UNC students search for rival team logos
Biggs, A. T., Spaventa, T., Hopfinger, J., & Mitroff, S. R. (2013, May). The effects of searching for something you love (or hate): Duke and UNC students search for rival team logos. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

As the visual world is too complicated to be processed in its entirety, it is important to understand why attention is guided to some aspects of a display, but not others. The study of attentional guidance has typically focused on two distinct classes of mechanisms: stimulus-driven (the physical properties of a visual display) and goal-driven (top-down intentions). However, there are aspects not addressed by this dichotomy (Awh, Belopolsky, & Theeuwes, 2012), and perhaps the most prominent is how an observer’s unique experiences and beliefs influence attentional allocation. Here, we examined "observer-driven" factors in visual search by testing observers from both Duke University and the University of North Carolina (UNC)—two schools with a long-standing sports rivalry. Participants included in the study were those who self-identified as fans of their own university and as strongly disliking the other university, and the question was whether these affiliations would affect attentional allocation. Participants completed a visual search task wherein they reported the presence or absence of one of three possible targets: the Duke logo, the UNC logo, or a familiar neutral logo (Georgia Tech). This design minimizes stimulus-driven differences as the same physical logos can engender different affective responses depending on the observers’ affiliations. When searching through arrays of unfamiliar team logos, the Duke and UNC participants were quicker to find both the Duke and UNC logos than the Georgia Tech logo. Moreover, the strength of the observers’ feelings towards Duke and UNC significantly affected their search efficiency—more extreme feelings (either positive or negative) produced shallower search slopes. These findings support a role for observer-driven differences in attentional allocation that goes beyond the traditional stimulus-driven versus goal-driven dichotomy.

Vision Sciences Society 2013

Visual expertise: Insights gained by comparing professional populations
Clark, K., Biggs, A. T., Darling, E. F., Cain, M. S., Jackson, T. H., Samei, E., Baker, J. A., & Mitroff, S. R. (2013, May). Visual expertise: Insights gained by comparing professional populations. Paper presented at the annual meeting of the Vision Sciences Society, Naples, FL

Professionals whose careers depend on visual skills typically demonstrate superior performance on career-related tasks; farmers better determine the sex of day-old chicks (Biederman & Shiffrar, 1987), and bank tellers better detect counterfeit currency (Klein, Gadbois, & Christie, 2004). Perceptual expertise has implications for learning and malleability, but the interpretation of expertise benefits is not straightforward. Complications arise, in part, because standard methodologies typically compare professionals to laypersons, raising concerns about confounding differences (e.g., motivation, speed/accuracy tradeoff, self-selection). Additionally, the mechanisms responsible for improvement may be ambiguous (e.g., enhanced sensory discrimination vs. improved strategies). To account for these issues, we analyzed performance across different professional groups on tasks related and unrelated to their careers. We assessed two groups of visual search experts (radiologists, airport security screeners), one group of facial symmetry experts (orthodontists), and one non-professional group (university participants). As expected, the professional groups demonstrated superior accuracy for career-related tasks (radiologists and airport security screeners for search, orthodontists for facial symmetry), and additional comparisons provided further insight. To evaluate potential differences in motivation, we compared performance on a task unrelated to the professionals’ expertise—temporal order judgment—and found no accuracy differences between professionals and non-professionals. Relatedly, comparisons between professional groups minimized speed/accuracy tradeoff concerns; professionals were slower on all tasks but only showed enhanced accuracy for career-relevant tasks. To elucidate whether benefits arose from self-selection or experience, we compared early- versus late-career individuals within the same profession and found differences related to amount of experience. Finally, we explored the nature of experts’ improvements and found evidence supporting superior top-down strategy selection (search professionals choose more effective strategies) as well as bottom-up stimulus-specific processing (orthodontists revealed enhanced symmetry discrimination for faces only). By comparing different types of experts on multiple tasks, we can better inform the nature of visual expertise.

Vision Sciences Society 2013

A common mechanism for percpetual reversals in motion-induced blindness, the Troxler effect, and perceptual filling-in
Devyatko, D., Appelbaum, L. G., & Mitroff, S. R. (2013, May). A common mechanism for percpetual reversals in motion-induced blindness, the Troxler effect, and perceptual filling-in. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

Several perceptual phenomena strikingly demonstrate that visible stimuli can fluctuate into and out of awareness; a physically available object will alternate between being perceived and being ‘invisible’ due to motion-induced blindness (MIB; Bonneh, Cooperman and Sagi 2001), the Troxler effect (TE; Troxler, 1804), and perceptual filling-in (PFI; Ramachandran and Gregory, 1991). There are clear differences between these three paradigms, but each produces a similar phenomenology. A common underlying mechanism responsible for the illusory disappearances has been proposed between MIB and PFI (Hsu, Yeh, Kramer, 2004) and PFI and TE (Komatsu, 2006; De Weerd, Smith and Greenberg, 2006), but it remains unknown how they all relate to one another. In the current study, participants (N=69) completed MIB, TE, and PFI paradigms — MIB: a yellow dot was imposed on a rotating grid of blue crosses; TE: a green dot was presented against a static gray background; PFI: a gray dot was presented against background noise. Two measures were calculated for each participant for each paradigm: the number of dot disappearances and the accumulated duration of the disappearances. To control for alternative explanations, eye movements were monitored and thresholds for the detection of motion coherence and changes in motion speed were determined for each participant. Significant correlations were found between the three paradigms for the number (r’s>0.48, p’s>0.001) and duration (r’s>0.34, p’s>0.01) of dot disappearances, and none of the effects were driven by eye movements or differences in motion coherence or speed perception thresholds. Principal component analyses conducted for the number and duration of disappearances revealed a single factor which explained a large proportion of the variance in MIB, TE, and PFI; 67% for the number and 60% for duration of disappearances. The results suggest a single oscillatory mechanism may underlie these diverse perceptual phenomena.

Vision Sciences Society 2013

Found targets are powerful distractors in multiple-target visual search
Cain, M. S., & Mitroff, S. R. (2012, November). Found targets are powerful distractors in multiple-target visual search. Poster presented at the annual meeting of the Psychonomic Society, Minneapolis, MN.

Multiple-target visual search—when more than one target can appear in a given search display—is a common type of real-world search in fields like radiology and baggage screening. Second targets are often missed in multiple-target searches, and we investigated why. Through three experiments we examined how the perceptual salience of the first target and memory for the first target affect subsequent search performance. Removing found first targets from the display, or making them salient and easily segregated color singletons, improved second-target accuracy. However, replacing found targets with random distractor items did not. Removing and highlighting found targets likely reduced both salience and memory effects, while replacing a target likely reduced salience, but not memory load—the first-target object file was likely updated but not discarded. Collectively, these experiments suggest that the working memory load of a first target has a larger effect on second-target accuracy than does its perceptual salience.

Psychonomic Society 2012

In search of experience effects: How TSA officers differ from undergraduates on visual search tasks
Mitroff, S. R., Biggs, A. T., Cain, M. S., Darling, E. F., Clark, K., Adamo, S. H., & Dowd, E. W. (2012, November). In search of experience effects: How TSA officers differ from undergraduates on visual search tasks. Paper presented at the annual meeting of the Psychonomic Society, Minneapolis, MN.

Visual search is a routine activity that people perform countless times each day. Search is also crucial for certain professions (e.g., airport security, radiology), and here we examine how the extensive practice gained through these careers alters search abilities. By comparing undergraduate participants from Duke University and Transportation Security Administration (TSA) officers at Raleigh-Durham Airport, we examine the effects of experience on visual search performance. In a laboratory we established at the airport, TSA officers completed search tasks and individual differences assessments during their normal work hours. Results from several search tasks demonstrated both similarities and differences in performance between the undergraduates and TSA officers; for example, the officers were more diligent searchers in a single-target search, but both populations showed performance decrements in multiple-target searches. By manipulating search parameters and experimental conditions (e.g., explicit instructions, time constraints), we reveal nuanced effects gained through visual search experience.

Psychonomic Society 2012

Cognitive and neural plasticity due to visual search training
Appelbaum, L. G., Clark, K., Mitroff, S. R., & Woldorff, M. G. (2012, October). Cognitive and neural plasticity due to visual search training. Paper presented at the annual meeting of the Society for Neuroscience, New Orleans, LA.

Successful visual search is the endpoint of a cascade of cognitive processes that includes attentional orienting, target discrimination, and response generation. These processes are in turn governed by underlying neural mechanisms that can be probed using cognitive neuroscience techniques. While it has become clear that performance on search tasks can improve with training, it is unclear which of the component subprocesses are changing with training to increase search proficiency. Here, we exploited the high temporal resolution of EEG, in combination with behavioral measures, to map out plasticity in the underlying cognitive and neural mechanisms resulting from extensive visual-search training. Our search tasks were specifically designed to enable extraction of several hallmark ERP markers of cognitive processes that might improve with training: the N2pc (attentional shifting to targets), the SPCN (manipulation and/or retention of information in visual short-term memory), and the LRP (preparation of motor response). Participants trained for 50 minutes on five consecutive days, viewing circular arrays of colored ellipses and reporting the orientation of a color-popout target as quickly and accurately as possible.

The results showed that response time (RT) decreased significantly across the training period by an average of 75 ms. Accuracy, however, remained high and unchanged across training, indicating the RT speeding was not at the expense of accuracy. ERP analyses comparing the first and last days showed that neither the amplitude nor latency of the N2pc component changed, signifying that the training-related RT improvement was not derived from accelerated attentional shifting with these stimuli. RT distribution analyses, however, did reveal significantly smaller N2pc amplitudes for slow versus fast trials before training, but not after, suggesting that some aspects of attentional orienting can be modulated by practice. The SPCN showed a particularly robust reduction in amplitude after training, supporting the hypothesis that practice facilitates target-discrimination processes requiring retention or manipulation of information in visual short-term memory. Lastly, the onset latency of the LRP was reduced by ~45 ms, revealing an overall facilitation of processing between the attentional shift and initiation of the motor response (presumably due faster discrimination), with the remaining ~30 ms of RT speeding presumably deriving from faster behavioral output after motor initiation. In sum, the present results delineate key phases of the stimulus-response processing chain that underlie visual-search improvements with training.

Society for Neuroscience 2012

Targets need their own personal space
Adamo, S. H., Cain, M. S., & Mitroff, S. R. (2012, May). Targets need their own personal space. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

Visual search is a critical task for many life-saving professions; Lifeguards scan for struggling swimmers, airport baggage screeners search luggage for dangerous items, and radiologists examine X-rays for tumors. While these jobs often require searching very cluttered environments for multiple targets (e.g., multiple tumors in an X-ray), most laboratory research is restricted to relatively uncluttered displays with only one target. It is known that clutter can negatively influence search (e.g., Verghese & McKee, 2003), and that a second target is less likely to be detected in a multiple-target search array when a first target has already been found (e.g., Tuddenham, 1962; Berbaum et al., 2010), but do these factors interact? Little is known about interactions between target number and visual clutter, and understanding this can inform both search theory and professional searches. Here we explored visual clutter in a multiple-target search paradigm where there could be 1 or 2 targets present on a given trial, and targets appeared in varying levels of clutter. Three categories of clutter were defined based upon the number of distractor items located within a 100-pixel radius from the center of a target—no clutter (no distractors within the radius), minimal clutter (1 distractor within the radius), and high clutter (2+ distractors within the radius). There was a significant interaction between target number (1 vs. 2) and clutter (no, minimal, or high): Clutter had no effect on detecting a single target or the first target in a dual-target trial, but clutter significantly reduced detection of a second target in a dual-target trial. Multiple-target search accuracy is highly sensitive to contextual influences (e.g., Cain, Dunsmoor, LaBar, & Mitroff, 2011), and the current results reveal a specific effect wherein relatively more difficult targets (i.e., the second target in a dual-target trial) are especially influenced by visual clutter.

Vision Sciences Society 2012

What eye-tracking can tell us about multiple-target visual search
Cain, M. S., Adamo, S. H., & Mitroff, S. R. (2012, May). What eye-tracking can tell us about multiple-target visual search. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

Many real-world visual searches contain multiple targets (e.g., a medical X-ray may have multiple tumors visible), and multiple-target searches present additional challenges beyond those of single-target searches. Specifically, finding one target can reduce the likelihood of finding a second target in the same array (a phenomenon dubbed ‘satisfaction of search’; Tuddenham, 1962), and this likelihood can be modulated by external factors such as anxiety (e.g., Cain, Dunsmoor, LaBar, & Mitroff, 2011). Multiple-target search effects have been examined in radiology (see Berbaum, et al., 2010) and in cognitive psychology (e.g., Fleck, Samei, & Mitroff, 2010), yet key questions remain about the underlying mechanisms. To address these questions, we utilized eye-tracking to provide insights into why targets are missed in multiple-target searches. Participants searched for perfect-T targets among pseudo-L distractors, with displays containing either 1 or 2 targets. Finding a first target in a multiple-target trial did not influence overall search performance (e.g., no change in average fixation time on distractors). However, analyses of the trials where the second target was missed revealed that: (1) second targets were not fixated on more than half of the multiple-target trials, and (2) when they were fixated, the average fixation length fell below the median fixation length for distractors. Collectively, this suggests that satisfaction of search is due, in part, to searchers not finding and fixating second targets long enough to determine their identity. These results present a different picture than previous radiological findings (Berbaum et al., 1998; Samuel et al., 1995), which found that missed targets were fixated the same amount of time regardless of whether or not another target had been detected. Satisfaction of search remains a very real problem, and these data suggest that the type of search and the searcher’s level of expertise may both play an important role.

Vision Sciences Society 2012

Neural correlates of learning during a visual search task
Clark, K., Appelbaum, L. G., Mitroff, S. R., & Woldorff, M. G. (2012, May). Neural correlates of learning during a visual search task. Paper presented at the annual meeting of the Vision Sciences Society, Naples, FL

Performance on visual search tasks can be improved with training; however, the neural mechanisms underlying such improvement are not clear. For example, although response times (RTs) typically shorten with training, it is unclear which components of the stimulus-response processing chain are facilitated and lead to the faster behavioral output. In principle, enhanced search abilities could result from improvements in various distinct cognitive stages along the stimulus-response processing chain, including: (1) faster attentional shifts to the target, (2) faster or better discrimination of the target, (3) faster motor-response preparation, and (4) faster response execution. To explore the loci of cognitive and neural plasticity resulting from visual-search training, we measured EEG as individuals performed a multi-day visual-search training protocol. Over the course of five days, we assessed changes in RTs and in various stimulus-processing-related ERP components: the N2pc (attentional shifting to target), the SPCN (manipulation and/or retention of information in visual short-term memory relevant for target discrimination processes), and the LRP (preparation for motor response). Participants were presented with circular arrays of colored ellipses and reported the orientation of a color-popout target as quickly and accurately as possible. Across the training period, RTs decreased by ~70ms. ERP analyses indicated that neither the amplitude nor latency of the N2pc component changed, suggesting that the training-related RT improvement did not derive from accelerated attentional shifting. In contrast, the onset latency of the LRP shifted earlier, suggesting improvement on the processing between the attentional shift and the motor-response initiation. Relatedly, the SPCN decreased substantially in amplitude with training, consistent with a facilitated target-discrimination process. Lastly the time between the LRP onset and the RT decreased, suggesting additional training effects on motor-execution speed. The present results thus help delineate several key phases of the stimulus-response processing chain that underlie visual search RT improvement with training.

Vision Sciences Society 2012

Attentional guidance by working memory overrides saliency cues in visual search
Dowd, E. W., & Mitroff, S. R. (2012, May). Attentional guidance by working memory overrides saliency cues in visual search. Paper presented at the annual meeting of the Vision Sciences Society, Naples, FL.

Visual search is influenced by a variety of factors, including how much the target stands out (i.e., its salience) and whether it is currently relevant (i.e., is it in working memory?). The contents of working memory are known to influence attention in simple visual search (Soto, Hodsoll, Rotschtein, & Humphreys, 2008). Furthermore, this memory influence likely occurs early in visual processing (Soto, Humphreys, & Heinke, 2006), as it can enhance efficient ‘pop-out’ search—wherein salient targets are detected almost automatically. Here we show that memory guidance can not only enhance but also reverse the capture of attention by visual salience. In a dual-task paradigm that combined working memory and multiple-target visual search, participants were first instructed to remember the rotation and orientation of a ‘T’ for a memory test at the end of the trial. During the retention interval, participants searched for target ‘T’s amongst distractor ‘L’s. Targets were either relatively dark, which made them highly salient against a white background, or relatively light and low-salient. In Experiment 1, working memory significantly guided search such that when the memory item matched a target, participants were more likely to find that specific target first, regardless of salience. Importantly, when the memory item did not match either target, participants found the high-salient target first, in keeping with a classic saliency effect. These results showed that the saliency effect was reversed via working memory biases. In Experiment 2, we amplified the saliency effect, such that the high-salient target was even easier to find. Participants were strongly biased to find the high salient ‘pop-out’ target first, yet this saliency effect was attenuated when the memory item matched the low-salient target. Collectively, these findings indicate that the deployment of attention in visual search is modulated by a balance between memory guidance biases and saliency cues.

Vision Sciences Society 2012

Visual search at the airport: Testing TSA officers
Mitroff, S. R., Biggs, A. T., Cain, M. S., Darling, E. F., Clark, K., Adamo, S. H., & Dowd, E. W. (2012, May). Visual search at the airport: Testing TSA officers. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

A significant challenge for laboratory-based research is to adequately replicate conditions found in the real world. Likewise, a challenge for field based research is to appropriately maintain the precision and control found within the laboratory. These hurdles are easily noticed when studying visual search, the act of finding a target amongst distractors. Decades of laboratory-based research have revealed many factors affecting visual search (see Nakayama & Martini, 2011 for a recent review); yet, these ‘sterile’ tasks conducted with novice participants can at times bear little resemblance to the tasks of professional searchers such as baggage screeners, radiologists, lifeguards, and military personnel. Conversely, conducting research with expert searchers in their natural environment can be logistically complex, which limits the scope of questions that can be asked. We are bridging this gap by conducting laboratory-based research with professional, expert searchers: employed Transportation Security Administration (TSA) officers at Raleigh-Durham International Airport. We have established a cognitive psychology laboratory within the airport, and the TSA officers participate in our research studies during their normal work hours. We are assessing a variety of visual and attentional abilities, including several measures of visual search. For example, in one task we employed a simplified visual search experiment to directly compare novice searchers (Duke University undergraduates) to expert searchers (TSA officers). Participants looked for ‘T’s amongst ‘L’s with set sizes of 8, 16, 24, and 32. Compared to undergraduates, TSA officers were slower to respond, with search slopes approximately 1.5 times larger. Importantly, the TSA agents were also more accurate at each set size, suggesting a greater search diligence. Through tasks such as these, combined with measures of individual differences (e.g., personality and clinical assessments), the goal of this project is to inform both cognitive theories of visual search and the TSA’s standard operating procedures.

Vision Sciences Society 2012

Improved visual cognition through stroboscopic training
Mitroff, S. R., Appelbaum, L. G., Schroeder, J. E., & Cain, M. S. (2011, November). Improved visual cognition through stroboscopic training. Paper presented at the annual meeting of the Psychonomic Society, Seattle, WA.

Fast-paced activities, such as those involved in competitive sports, place great demands on vision. As such, much can be gained by enhancing visual cognition abilities. We provide evidence for improved performance via stroboscopic visual training. Individuals were divided into an experimental group that trained with stroboscopic eyewear and a control group that trained with identical eyewear that contained transparent lenses. The stroboscopic eyewear (Nike Strobes) was equipped with lenses that alternated between transparent and opaque states. Participants included Duke University varsity and club sport athletes and non-athletes. Training varied across these populations to suit the individuals, and ranged from 2 to 10 training sessions. Computer-based assessments were administered pre- and post-training. One assessment revealed lowered motion coherence thresholds for the experimental group, suggesting increased motion sensitivity. Another revealed an improved ability in the experimental group to accurately identify visual information that was presented for approximately 100ms. Along with other measures, these results suggest that stroboscopic training can improve visual cognition.

Psychonomic Society 2011

Optimal models of human multiple-target visual search
Cain, M. S., Vul, E., Clark, K., & Mitroff, S. R. (2011, July). Optimal models of human multiple-target visual search. Paper presented at the 33rd Annual Conference of the Cognitive Science Society. Boston, MA

Unlike laboratory experiments, real-world visual search can contain multiple targets. Searching for an unknown number of targets creates a unique set of challenges for the observer, and often produces serious errors. We propose a Bayesian optimal foraging model to predict and describe behavior in such search scenarios, and investigate whether people adapt their search strategies based on complex statistics of target distributions. Separate groups searched arrays drawn from three target distributions with the same average number of targets per display, but different target-clustering properties. As predicted, participants searched longer when they expected more targets to remain and adjusted their expectations as searches unfolded, indicating that searchers are sensitive to the target distribution, consistent with both an optimal foraging framework and an ideal Bayesian observer. However, compared to the ideal observers, searchers systematically under-adjusted to the target distribution, suggesting that training could improve multiple-target search in radiology and other crucial applications.

Annual Conference of the Cognitive Science Society 2011

Interactions between reward, feedback, and timing structures on dual-target search performance
Clark, K., Cain, M. S. Adcock, R. A., & Mitroff, S. R. (2011, May). Interactions between reward, feedback, and timing structures on dual-target search performance. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

Individuals who conduct visual searches that can contain more than one target face many challenges. Such multiple-target visual searches can be especially error prone, as identification of one target often makes identification of a second target less likely. Given that many real-world searches can be multiple-target searches (e.g., radiological examinations, baggage screening, military searches), it is important to understand what can affect performance. Multiple-target search is particularly sensitive to top-down influences such as anticipatory anxiety (Cain, Dunsmoor, LaBar, & Mitroff, VSS 2011), and here we explore the impact of reward motivation. Participants completed a paradigm that reliably produces dual-target errors (Fleck, Samei, & Mitroff, 2010). When we simply motivated participants with a performance-based, ten-percent chance of winning an additional &dollar;50 in compensation (Experiment 1), the performance decline on dual-target trials was eliminated, while accuracy on single-target trials remained the same. Further, without monetary motivation, adding trial-by-trial feedback (Experiment 2) did not significantly improve dual-target accuracy; however, the presence of both monetary motivation and feedback (Experiment 3) resulted in substantial performance benefits for both single- and dual-target conditions compared to Experiments 1 and 2. Finally, in the presence of top-down monetary motivation, trial-based time limits (Experiment 4) did not affect performance (i.e., participants performed equivalently with or without a time limit). This is in contrast to prior data without monetary incentives (Fleck et al., 2010), in which time limits negatively affected performance. Collectively, these experiments demonstrate that (1) motivation alone is sufficient to enhance dual-target search performance, (2) such benefits are enhanced when paired with trial-by-trial feedback, and (3) time limits hurt performance in the absence of motivation but have no effect with motivation. These findings provide key information about the role of top-down motivation on performance and how this can successfully improve performance on critical dual-target searches.

This work was supported by the Army Research Office (#54528LS) and through a subcontract with the Institute for Homeland Security Solutions (IHSS).

Vision Sciences Society 2011

Impact of media multitasking on attentional filtering and disengagement
Cain, M. S., & Mitroff, S. R. (2010, November). Impact of media multitasking on attentional filtering and disengagement. Poster presented at the annual meeting of the Psychonomic Society, St. Louis, MO.

People have nearly constant access to media and electronic sources of information. Whereas some people often consume multiple sources simultaneously, others regularly consume one source at a time. Recent research has shown that individual differences in trait media multitasking relate to the ability to filter distracting information (Ophir, Nass, & Wagner, 2009). We reveal that these differences occur at the level of attention. Using a singleton distractor task, we found that heavy media multitaskers do not take advantage of information that would allow them to selectively ignore an irrelevant color singleton to the same degree as light media multitaskers do. Furthermore, in a related task, we have found that heavy media multitaskers take more time to inhibit planned responses, suggesting a deficit in disengaging from salient stimuli. Complex everyday activities, such as consuming multiple media simultaneously, may have measurable impacts on basic attentional processes.

Psychonomic Society 2010

Identifying and reducing satisfaction of search errors: How to alleviate dual-target search costs
Mitroff, S. R., Clark, K., & Cain, M. S. (2010, November). Identifying and reducing satisfaction of search errors: How to alleviate dual-target search costs. Paper presented at the annual meeting of the Psychonomic Society, St. Louis, MO.

Some occupations (e.g., airport luggage screeners, military personnel, radiologists) require highly accurate visual searches. To maximize performance, it is important to identify factors that decrease accuracy and then identify means to alleviate their detrimental effects. One negative factor on search accuracy is satisfaction of search (SOS)—when the successful detection of a search target reduces the detectability of a second target present in the same array. Our prior work (Fleck, Samei, & Mitroff, 2010) suggests that SOS arises when searchers have an expectation about the likelihood of a given target type being present and when they are under pressure to perform quickly. We introduce new evidence that SOS errors are eliminated when ambiguity between potential targets and distractors is removed and are modulated by expectations about target prevalence. We provide a clearer picture of the pressures that engender SOS by examining those factors that both provoke and alleviate the effect.

Psychonomic Society 2010

Distractor filtering in media multitaskers
Cain, M. S., & Mitroff, S. R. (2010, May). Distractor filtering in media multitaskers. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL

Despite the near-ubiquity of visual search, performance can differ wildly from person to person, especially under distracting conditions. Recent research suggests that extensive exposure to certain everyday activities (e.g., playing action video games, speaking a second language, media multitasking) may be able to enhance search performance. Here we explored individual differences in frequency of media multitasking (e.g., watching TV while reading or playing video games while talking on the phone) to investigate whether this common behavior can impact the ability to filter out distractions during visual search. Participants searched simple arrays of objects for a shape singleton (i.e., a circle among squares). Half the arrays also contained a color singleton (i.e., a red shape among green shapes). Each participant completed two conditions; in the ‘Never’ blocks participants were instructed that the color singleton distractor would never be the target shape singleton, and in the ‘Sometimes’(tm) blocks they were instructed that it could sometimes be the target. Previous work has shown that participants can successfully use this instructional information to improve performance in Never blocks by exercising top-down control to filter out irrelevant singletons. Here we found that overall (collapsed across blocks), media multitaskers responded more quickly than non-multitaskers. z-Transformed results revealed specific ways participants differed; in the Never blocks multitaskers performed relatively worse than non-multitaskers when distractors were present, but both groups showed comparable distractor-related slowdowns in the Sometimes blocks when top-down distractor filtering was not necessary. These results suggest that media multitaskers did not use the information about the distractor'(tm)s irrelevance in the Never blocks to filter it out to the same degree as non-multitaskers. This is consistent with the idea that those who routinely consume multiple media in daily life demonstrate poorer filtering of irrelevant information in a laboratory setting.

Vision Sciences Society 2010

Generalized ‘satisfaction of search’: Adverse influences on dual-target search accuracy
Fleck, M. S., Samei, E., & Mitroff, S. R. (2009, November). Generalized ‘satisfaction of search’: Adverse influences on dual-target search accuracy. Paper presented at the annual meeting of the Psychonomic Society, Boston, MA. (presented by S. R. Mitroff)

The successful detection of a target in a radiological search can reduce the detectability of a second target, a phenomenon termed “satisfaction of search” (SOS). Here, we investigate the generality of SOS to simultaneously inform radiology, cognitive psychology, and nonmedical, real-world searches. Our experiments, utilizing nonmedical searches and untrained searchers, suggest that SOS is affected by several factors, including (1) relative salience and frequency of different target types, (2) time pressure, (3) perceptual set, (4) search instructions, and (5) reward pressure. Collectively, SOS arises when searchers have an expectation about the likelihood of a target type and when they are under pressure to perform quickly. This first demonstration of SOS outside of radiology might implicate a default heuristic that could affect search broadly. For example, the present data suggest that the detection of easyto-spot targets in baggage screening (e.g., water bottles) might reduce detection of hard-to-spot targets (e.g., box cutters).

Psychonomic Society 2009

Motion Induced Blindness: The more you attend the less you see
Carter, O., Luedeman, R., Mitroff, S. R., Nakayama, K. (2009, September). Motion Induced Blindness: The more you attend the less you see. Paper presented at the 32nd Annual Meeting of the Japan Neuroscience Society, Nagoya, Japan.

During motion induced blindness (MIB), visually salient objects vanish from awareness when presented on a background of motion. We conducted 3 psychophysical experiments looking at the effect of increasing target number, directed attention toward one target and reducing the amount of attention with a demanding secondary task at fixation. Together the results from all 3 experiments indicate that, awareness is indeed influenced by the same factors associated with attention. In every case, however, the relationship was seen to be in a negative direction. The more attention available for each target during MIB, the more it was suppressed from awareness. For all 3 experiments, a simulated MIB condition, ruled out the effect of task difficulty or response inaccuracy. A number of mechanisms are considered to explain this surprising effect.

Japan Neuroscience Society 2009

Effects of videogame expertise on change detection abilities
Clark, K., Fleck, M. S., & Mitroff, S. R. (2009, May). Effects of videogame expertise on change detection abilities. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

As our everyday lives become increasingly more complex with technological advancements, an important question arises in whether certain experiences can lead to improved cognitive and perceptual abilities. Recent research has demonstrated that action videogame players (VGPs) consistently demonstrate improved performance across a variety of visual and attentional tasks when compared to non-videogame players (NVGPs; e.g., Green & Bavelier, 2003). Videogame exposure is thought to heighten and hone attentional abilities, thus guiding and enhancing performance in visually demanding tasks. Yet, it remains unknown how and why such benefits arise. To explore the causal mechanisms that could underlie the VGPs' improved abilities, we tested VGPs and NVGPs on a modified version of a change-detection ‘flicker task’ (previously used in Mitroff & Simons, 2002). In this paradigm, participants briefly view a scene, which is followed by a blank display, a modified version of the scene, and finally another blank display. Participants are to identify the location of the change between the two scenes. In a typical flicker task, this change sequence continuously repeats until detection, but in this modified version, participants make a localization response after each change presentation. When participants do not detect the change, they are to guess, thus providing several guessed locations leading up to their eventual detection. VGPs successfully detected a higher percentage of changes and did so in fewer presentations than NVGPs, consistent with prior claims of enhanced perceptual abilities in VGPs. Further analyses revealed different strategies wherein VGPs were more diligent in their searching; when participants happened to accurately guess the change location, VGPs were more likely notice the change, whereas the NVGPs were more likely to continue searching for the change without noticing their happenstance detection. These results suggest that both enhanced search strategies and search abilities drive the VGPs' benefits.

Vision Sciences Society 2009

Multisensory benefits of playing video games
Donohue, S. E., Woldorff, M. G., & Mitroff, S. R. (2009, May). Multisensory benefits of playing video games. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

A fundamental aspect of perception is the rapid and reliable combination of sensory information from multiple modalities. Accurate perception of a given multisensory object is therefore highly reliant on the ability to analyze and compare the temporal and spatial information of the input from each modality such that their correspondence is correctly computed. Previous studies have shown that playing video games enhances visual attention as well as visual perception (e.g., Green & Bavelier, 2003; 2007). However, considering that video games are typically multisensory in nature, containing both auditory and visual components, their influence seems likely to reach beyond unimodal visual effects and to alter the processing of multisensory information more generally, a realm that has been little investigated. To address this, we presented subjects with auditory and visual stimuli occurring at varying stimulus onset asynchronies (SOAs) in 50ms increments, from the auditory stimulus (a tone) coming 300ms before the visual (a checkerboard) to 300ms after. Subjects participated in a simultaneity judgment task (did the stimuli appear at the same time or at different times?) and a temporal-order judgment task (which stimulus came first?). For the simultaneity judgment task, non-video-game players showed a broader and more asymmetric window of integration, as they were more likely than video-game players to report the stimuli as simultaneous when the auditory followed the visual. In the temporal-order judgment task, video-game players were more accurate than non-video-game players at the most difficult SOAs (those close to simultaneous). No between-group differences in response times were observed; however, all subjects responded more slowly at the most difficult SOAs. Together, these results suggest that the benefits of playing video games occur not only in the visual modality, but they can also impact the processing of multisensory information, including by altering one's temporal window and accuracy of multisensory integration.

Vision Sciences Society 2009

See an object, hear an object file: Object correspondence transcends sensory modality
Jordan, K. E., Clark, K., & Mitroff, S. R. (2009, May). See an object, hear an object file: Object correspondence transcends sensory modality. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL.

An important task of perceptual processing is to parse incoming information from the external world into distinct units and to subsequently keep track of those units over time as the same, persisting internal representations. Within the realm of visual perception, this concept of maintaining persisting object representations has been theorized as being mediated by “object files” - episodic representations that store (and update) information about objects' properties and track objects over time and motion via spatiotemporal information (e.g., Kahneman et al., 1992). Although object files are typically conceptualized as visual representations, here, we demonstrate that object-file correspondence can be computed across sensory modalities. We employed a novel version of the object-reviewing paradigm: Line-drawn pictures (e.g., a phone and a dog) were briefly presented within two distinct objects in a preview display. Once the pictures disappeared, the objects moved (to decouple objecthood from location) and then a sound (e.g., a dog bark) occurred. The sound was localized to the left or right of the display, corresponding to the end locations of the two objects. Participants were instructed to indicate whether the sound matched either preview picture or whether it was novel (e.g., a dog bark would “match” if either preview picture was a dog). Participants were significantly faster to respond when the sound occurred with the object originally containing the associated picture compared to when the sound occurred with the other object. This significant response time benefit provides the first evidence for visual and auditory information working in tandem to underlie object-file correspondence. An object file can be initially formed with visual input and later accessed with corresponding auditory information. Object files may thus operate at a highly abstract level of perceptual processing that is not tied to specific modalities.

Vision Sciences Society 2009

Generalization of human fear learning along a perceptual gradient of expression intensity
Dunsmoor, J. E., Mitroff, S. R., & LaBar, K. S. (2008, November). Generalization of human fear learning along a perceptual gradient of expression intensity. Poster presented at the annual meeting of the Society for Neuroscience, Washington, DC.

Despite its theoretical relevance to understanding anxiety disorders, the role of generalization in the acquisition and expression of learned fear has received sparse attention in human conditioning research. Generalization processes may help explain how neutral stimuli, never paired with an aversive stimulus, come to elicit a fear response by sharing features with a fear-conditioned stimulus. In animal studies, generalization gradients have been characterized by comparing behavioral responses to non-conditioned stimuli as a function of their perceptual similarity to a conditioned stimulus. However, generalization gradients of conditioned fear learning along perceptual continua have yet to receive a systematic examination in humans.
The present study investigated the extent to which conditioned fear responses generalize to faces that display differing amounts of fear intensity. Stimuli consisted of five graded emotionally expressive faces of the same actor, ranging from neutral to fearful. Three experimental training phases were conducted: pre-training baseline, discrimination training, and a generalization test. During pre-training, all facial expression values were presented without reinforcement in a pseudorandom order. During discrimination training, mild electrical wrist stimulation was paired with the intermediate-intensity face stimulus (55% fear value), and the face with the extreme intensity value served as an unreinforced control. The magnitude of fear responses to all stimuli prior and subsequent to discrimination training was assessed using skin conductance response (SCR). Results showed that prior to discrimination training, all stimuli evoked relatively low and undifferentiated SCRs. Following discrimination training, a gradient was observed such that SCRs generalized to non-reinforced faces as a function of both perceptual similarity to the reinforced stimulus and emotional intensity. Although most studies of fear conditioning have focused on the predictive relationship between the conditioned and unconditioned stimulus presented during acquisition training, these findings reveal that perceptually similar stimuli never paired with aversive reinforcers can evoke sizable generalized fear responses. This novel approach to measuring generalized fear may help elucidate the conditions under which anxiety disorders marked by emotional over-responding, such as posttraumatic stress disorder, are manifested.

Society for Neuroscience 2008 and North Carolina Cognition Conference

V1 population response to changes in direction of stimulus motion: modeling and perception
Wu, W., Tiesinga, P. H., Tucker, T. R., Mitroff, S. R., Heiner, J. A., & Fitzpatrick, D. (2008, November). V1 population response to changes in direction of stimulus motion: modeling and perception. Poster presented at the annual meeting of the Society for Neuroscience, Washington, DC.

Under natural viewing conditions, circuits in primary visual cortex (V1) must represent the information contained in a continuous stream of images that often contains abrupt changes in stimulus properties. Studies of V1 cortical response to changes in direction of stimulus motion using voltage-sensitive dye imaging have shown that the dynamics of the population response vary as a function of direction deviation angle (Wu et al., 2007, Soc. Neurosci. #715.9). For direction deviation angles smaller than 90º, the peak direction sweeps smoothly from the initial direction to the final direction. For direction deviation angles larger than 112.5º, the peak direction transiently deviates away from the direction of the second stimulus, then exhibits a step function that transiently overshoots and then settles on the final direction. The dynamics of peak amplitude also vary as a function of direction deviation angle. There is often a “notch” during the transition which is largest when the direction deviation angles are near 90º.
Surprisingly, much of the complexity of the population response dynamics could be explained by a simple linear summation model. However, the transition in cortical response found with small direction deviation angles was smoother than that predicted by summation of the actual cortical response to individual stimulus components.

The dynamics of the population response predict distortions in the perceived direction of stimulus motion that depend on the angle of deviation. For small direction deviation angles, the perceived motion trajectory is predicted to be smoother than the real stimulus trajectory. In contrast, for large direction deviation angles, the perceived motion trajectory is predicted to be sharper than the real stimulus trajectory. To test the predictions, we designed a psychophysics experiment that follows the two-alternative forced choice (TAFC) paradigm. Our results suggest distortions in the perception of motion trajectory that are consistent with the predictions from population response dynamics.

Society for Neuroscience 2008

Motivational benefits of video game playing
Mitroff, S. R. (2008, November). Motivational benefits of video game playing. Paper presented at the annual meeting of the Psychonomic Society, Chicago, IL.

Prior research (e.g., Green & Bavelier, 2003) has shown that, as compared with non–videogame players (NVGPs), videogame players (VGPs) possess enhanced visual attention and perceptual abilities. Benefits are found for a variety of individuals and can result from training: with minimal videogame exposure, NVGPs can improve on the same tasks, suggesting a causal effect of videogame play. However, it remains unclear why and how these effects arise. I present a series of experiments that explore the cognitive mechanisms that guide VGPs’ benefits and suggest that VGPs gain, in part, from a heightened level of motivation and arousal. Beyond changes to attentional and perceptual abilities, videogame playing may boost motivation and arousal, which in turn can guide more optimized strategy choice and learning. For example, in visual search, I find that VGPs will introduce their own “speed–accuracy trade-off ”; in difficult situations, they will slow their rate of responding to raise their accuracy.

Psychonomic Society 2008

Motion induced blindness: The more you attend the less you see
Carter, O., Luedeman, R., & Mitroff, S. R., & Nakayama, K. (2008, May). Motion induced blindness: The more you attend the less you see. Paper presented at the annual meeting of the Vision Sciences Society, Naples, FL.

During motion induced blindness (MIB), visually salient objects vanish from awareness when presented on a background of coherent motion. Here we investigate the influence of item-number, group-number and attentional demand on the perceptual disappearance of individual stimulus targets. In Experiment One, 1–4 square targets (varying in color and angular rotation) were each presented centered within one of the four visual quadrants. Disappearance of a single target presented alone averaged 23.4% of the 40 second trials. Surprisingly, the total proportion of disappearance increased only moderately to 28.7% when the maximum number of 4 targets was presented, while the disappearance of any individual target, reduced by more than half to an average of 11.4% of the trial. In Experiment Two, the effect of group number was considered. In every trial, all 4 target squares were presented within the same quadrant. Targets defined as “in-group” shared feature properties (color, texture, proximity and alignment of border contours), “out-group” targets differed in respect to all features. Despite only moderate effects of the grouping cues (i.e., simultaneous disappearance of all 4 targets only increased from 0.5% when targets formed 4 out-groups to 2% when targets formed a single group), an increase in group number lead to greater total disappearance without any associated increase in the disappearance of the individual targets. In Experiment Three, we selectively manipulated attentional load with a central detection task. Subjects reported less disappearance of a single target in high attention conditions relative to fixation and low attention conditions. In all experiments, a simulated MIB condition ruled out the effect of task difficulty or response inaccuracy. Together these results indicate a striking paradox: the more attention allocated towards a target object, the more it will be suppressed from awareness. A number of mechanisms are considered to explain this surprising effect.

Vision Science Society 2008

Videogamers excel at finding rare targets
Fleck, M. S., & Mitroff, S. R. (2008, May). Videogamers excel at finding rare targets. Poster presented at the annual meeting of the Vision Sciences Society, Naples, FL

Important real-world visual searches often operate with rarely present targets. For example, targets are seldom present in airport baggage X-ray screening, radiology, and aircraft inspection. Disturbingly, rare target searches can produce high miss rates when observers proceed too quickly. The low frequency of targets causes searchers to abort searches more and more rapidly, ultimately causing numerous motor errors and incomplete scanning of the display. Here we demonstrate that individuals with extensive videogame experience perform much more accurately on such rare target visual searches than individuals without any videogame experience. This significant accuracy benefit for videogame players (VGPs) over non-videogame players (NVGPs) derives largely from a top-down, strategic slowing of responses, countering the typical speed-up observed in rare target search. Although all participants were allowed as much time as desired for each search array, VGPs avoided the pitfall of responding too quickly in low frequency conditions, whereas NVGPs sped up and consequently yielded the typical speed-accuracy trade-off. Even under conditions of faster responding, VGPs continued to perform more accurately than NVGPs, potentially highlighting a bottom-up, response-based advantage. These findings demonstrate that videogame expertise accurately predicts higher performance on rare target search, suggesting important implications for real-world search tasks with similar low target probabilities.

Vision Science Society 2008

Staying in Bounds: Contextual constraints on object file coherence
Mitroff, S. R., Arita, J. T., & Fleck, M. S. (2007, November). Staying in Bounds: Contextual constraints on object file coherence. Paper presented at the annual meeting of the Psychonomic Society, Long Beach, CA.

Coherent visual perception necessitates the ability to track objects as the same entities over time and motion. Calculations of such object persistence are constrained by specific rules and here we explore these rules through object files: visual representations that track entities over time and motion as the same persisting objects and store information about the objects. We present three new findings. First, objects files are constrained by “boundedness”; persisting entities should maintain a single closed contour. Second, object files are constrained by “containment”; all the properties of a persisting object should reside within the object itself. Third, object files are sensitive to the context in which an object appears; the same physical entity that can instantiate object-file formation in one context cannot in another. This contextual influence demonstrates for the first time that object files are sensitive to more than just the physical properties contained within any given display.

Psychonomic Society 2007

Catching a miss: Error reduction in low prevalence search
Fleck, M. S., & Mitroff, S. R. (2007, May). Catching a miss: Error reduction in low prevalence search. Poster presented at the annual meeting of the Vision Sciences Society, Sarasota, FL

Failing to find a tumor in an X-ray scan or a gun in an airport baggage screening can have dire consequences, yet error rates in such tasks are alarmingly high. These visual searches are alike in that they involve detecting very rare targets, yet there is conflicting evidence about whether this factor of target prevalence is indeed causally linked to high error rates. The present study reconciles the disparate findings by revealing that prevalence-related increases in misses are attributable specifically to response execution errors, not perceptual or identification errors. When targets are rarely presented in a visual search, observers adapt by responding more quickly, which in turn leads to high error rates. However, when offered the opportunity to correct their mistakes, observers can largely eliminate such action-based errors, and in doing so no longer exhibit high miss rates during low-prevalence search. Observers participated in one of two conditions: the No-Correction condition, a replication of Wolfe, Horowitz, & Kenner (2005), or the Correction condition, an identical design except the observers were provided with the option to change their last response during the subsequent trial. Whereas the No-Correction condition confirmed previous results showing increasing error rates with decreasing target prevalence, this relationship was entirely abated in the Correction condition by observers catching their own mistakes. Accuracy and response time data support that faster speeds lead to error, that observers are cognizant of their execution-based errors, and that such mistakes are correctable. The results motivate a shift towards exploring contributions to high error rates in real-world searches beyond target prevalence.

Vision Sciences Society 2007

Preserved visual representations despite change blindness in 11-month-old infants
Mitroff, S. R., & Wang, S. (2007, May). Preserved visual representations despite change blindness in 11-month-old infants. Poster presented at the annual meeting of the Vision Sciences Society, Sarasota, FL.

The nature of visual representations remains an unanswered question. Whereas some change detection research might suggest that visual representations are fleeting and sparse, recent findings demonstrate that change blindness can result from a failure to compare available representations rather than from a failure to form representations. Observers can miss a change but still have access to the pre- and post-change information, suggesting representations can be robust, even if they are not compared to one another (Mitroff, Simons, & Levin, 2004). Here we find comparable results with infants — when they fail to notice a physical change, they nonetheless remember both the pre- and post-change information. Wang and Baillargeon (2006) showed 11-month-old infants an event in which an opaque tall cover was lowered over a short block. When the cover was lifted to reveal that the block had become much taller, the infants did not look longer than if the block were uncovered as the same height, suggesting they failed to detect the change. (When the block was hidden behind the cover through occlusion, however, the infants nevertheless detected the change.) Here we presented 11-month-old infants with a change from a short to a tall block through covering, but then administered to them a preferential-looking task: On alternating trials they were shown the short and a medium block, or the tall and a medium block. All blocks were identical except in height. Consistent with the view of maintained representations despite change blindness, the infants looked longer at the medium block than at either of the previously seen ones (a classic novelty preference revealing memory for the short and tall blocks). These results are developmentally significant, demonstrating an infant-adult parallel, and are also informative for the nature of visual representations, showing limited performance in infants does not necessarily reveal a representational failure.

Vision Sciences Society 2007

Space and time, not surface features, underlie object persistence
Mitroff, S. R., & Alvarez, G. A. (2006, November). Space and time, not surface features, underlie object persistence. Paper presented at the annual meeting of the Psychonomic Society, Houston, TX.

Successful visual perception relies on the ability to keep track of distinct entities as the same objects persisting from one moment to the next. This is a computationally difficult process, and its underlying nature remains unclear. Here, we use the object file framework to explore whether surface feature information (e.g., color, shape) can be used to compute such object persistence. In three experiments using a wide variety of surface feature information, including color, shape, size, luminance, and topography, we find that spatiotemporal information (location as a function of time) easily determines object files, but surface features do not. The results suggest a strong constraint on the visual system’s ability to compute object persistence.

Psychonomic Society 2006

Staying in bounds: A critical role of closure for object files
Arita, J. T. & Mitroff, S. R. (2006, May), Staying in bounds: A critical role of closure for object files. Poster presented at the annual meeting of the Vision Sciences Society, Sarasota, FL.

As we move around the world, and the world around us, we must continually track objects as being the same entities from one moment to the next. But, over what sorts of entities can such ‘object persistence’ be computed? Previous work with adults and infants has shown that one of the most important principles for determining objecthood is cohesion: objects must have and maintain a unified boundary. For example, rarely do real objects suddenly split in two. But what happens if that boundary does not exist in the first place? Here we directly explore one particular aspect of cohesion; the role of closure: must objects have a continuous, single boundary? We examined this by contrasting objects defined by illusory contours (i.e., a Kanizsa square) with objects defined by physical contours. While both conditions involve subjective objects, only one adheres to the principle of closure. We explored the effects of closure on ‘object file’ representations by measuring ‘object specific preview benefits’ (OSPBs) wherein a preview of information on an object leads to a speeded response when that information later reappears on the same object (compared to when it reappears on a different object), beyond display-wide priming. A significant OSPB was found for objects defined by physical contours, but not for objects defined by illusory contours (and the conditions were significantly different from one another). This suggests that closure, per se, may play an especially important role in object persistence.

Vision Sciences Society 2006

Reversing how to think about ambiguous figure reversals: Spontaneous alternating by uninformed observers
Mitroff, S. R., Sobel, D. M., Gopnik, A. (2006, May). Reversing how to think about ambiguous figure reversals: Spontaneous alternating by uninformed observers. Poster presented at the annual meeting of the Vision Sciences Society, Sarasota, FL.

Ambiguous figures, such as the Necker Cube or ‘duck-rabbit,’ are a special class of images that can give rise to multiple interpretations. Traditionally, switching between the possible interpretations of an ambiguous figure, or reversing one's interpretation, has been attributed to either top-down or bottom-up processes (e.g., either attributed to having knowledge of the nature of the ambiguity or attributed to a form of neuronal fatigue). However, here we present evidence that is incompatible with both sorts of explanations. Five- to nine-year old observers participated in four tasks - an ambiguous figures reversal task, two ‘Theory of Mind’ tasks, and a Piagetian number conservation task (the last being used as a measure of general cognitive abilities). Going against purely top-down explanations, one third of the observers reversed the ambiguous figures when completely uninformed about the ambiguity. Further, going against purely bottom-up explanations, those children who made these ‘spontaneous’ reversals were more likely to succeed on a high-order theory of mind task, even when factoring out general cognitive abilities. These findings suggest that reversing between the possible percepts of a bi-stable image can occur spontaneously and raise the possibility of there being necessary, but not sufficient, cognitive conditions for reversals to occur.

Vision Sciences Society 2006

One plus one equals one: The effects of merging on object files
Mitroff, S. R., Scholl, B. J., & Wynn, K. (2005, November). One plus one equals one: The effects of merging on object files. Poster presented at the annual meeting of the Psychonomic Society, Toronto, ON, Canada.

A critical task in visual processing is keeping track of objects as the same persisting individuals over time, and these operations can be assessed in terms of the effects of various manipulations on mid-level object file representations. Here, we explore perhaps the most important principle of object persistence: Objects must maintain a single unified boundary over time (the cohesion principle). We do so by measuring object-specific preview benefits (OSPBs), wherein a preview of information on a specific object speeds the recognition of that information at a later point, when it appears again on the same object. Object files were dramatically affected when two objects smoothly merged into one: The information from only one object survived this cohesion violation to produce an OSPB (whereas OSPBs from both original objects remained in control displays without cohesion violations). These results demonstrate the power of the cohesion principle in the maintenance of mid-level visual representations.

Psychonomic Society 2005

Online grouping and segmentation without awareness: Evidence from motion-induced blindness
Mitroff, S. R. & Scholl, B. J. (2004, May). Online grouping and segmentation without awareness: Evidence from motion-induced blindness. Paper presented at the annual meeting of the Vision Sciences Society, Sarasota, FL.

The visual system must parse and group the incoming input into discrete units, but it has proven difficult to determine when and how this occurs. Here we show that both object and group representations can be formed, disrupted, and updated without awareness. We do so using the phenomenon of motion-induced blindness (MIB), wherein salient and attended objects will fluctuate into and out of conscious awareness when superimposed onto certain global moving patterns. Previous research has shown that both objecthood and grouping influence MIB. For example, two discs will tend to enter and leave awareness simultaneously if grouped into a single unit (even by cues such as proximity), but will otherwise tend to undergo MIB independently. Here we alter various segmentation and grouping cues while two discs are unseen during MIB, and find that such changes influence whether the discs reappear independently. For example, adding a line to form a dumbbell during MIB causes two discs to reenter awareness together. Similarly, when the connecting line of an initial dumbbell is removed during MIB, the discs reappear independently. These results indicate that object representations can be formed and disrupted outside of awareness. Similar effects occur with grouping cues such as proximity. Observers viewed three evenly-spaced discs in a horizontal line, and reported when all three disappeared due to MIB. At this point — while the discs were present but unseen — a single randomly chosen disc gradually faded out, leaving two discs which were either close together or separated. Separated discs tended to reenter awareness independently, whereas neighboring discs reappeared simultaneously, indicating that their grouping strength had been revised outside of awareness. In these and several other examples, we illustrate how MIB can be used as a tool to determine the importance of conscious awareness for several types of visual processing.

Vision Sciences Society 2005

The relationship between object files and conscious perception
Mitroff, S. R., Scholl, B. J., & Wynn, K. (2003, May). The relationship between object files and conscious perception. Poster presented at the annual meeting of the Vision Sciences Society, Sarasota, FL.

Many aspects of mid-level vision appear to operate on the basis of representations which precede identification and recognition, but in which discrete objects are segmented from the background and tracked over time (unlike early sensory representations). It has become increasingly common to discuss such phenomena in terms of ‘object files’ (OFs) — critical mid-level representations which help mediate our conscious perception of persisting objects — e.g. telling us ‘which went where’. Despite the appeal of the OF framework, it remains unclear to what degree OFs underlie consciously perceived object trajectories. Here we present at least one case wherein conscious percepts of ‘which went where’ in dynamic displays diverge from the computation of ‘which went where’ in the OF system. Observers viewed an ambiguous ‘bouncing/streaming’ display in which two identical objects moved such that they could have either streamed past or bounced off each other. We measured two dependent variables: (1) an explicit report of perceived bouncing or streaming; and (2) an implicit object-specific priming (OSP) measure, wherein a ‘preview’ of information on a specific object — e.g. a letter that flashes inside a small box — speeds the recognition of that letter at a later point when it appears again on the same box (compared to when it reappears on a different box). When the displays were manipulated such that observers had a strong bias to perceive streaming (on over 90% of the trials), there was nevertheless a strong *negative* OSP associated with the streaming motion, such that the OSP appeared to have ‘bounced’ even though the percept ‘streamed’. Given that OSP measures have been taken as a hallmark of the operation of object files, this suggests that in at least some cases conscious percepts of ‘which went where’ in dynamic ambiguous displays can override the mapping computed by the object-file system.

Vision Sciences Society 2003

A lack of confidence in implicit change detection
Mitroff, S. R. & Simons, D. J. (2001, May). A lack of confidence in implicit change detection. Poster presented at the annual meeting of the Vision Sciences Society, Sarasota, FL.

Purpose: Two recent studies suggest that explicit measures of change detection may overestimate change blindness. First, when observers reported no explicit awareness of a change, their response latency was still affected by the presence of the change (Williams and Simons 2000). Second, without explicit awareness of a change, the identity of a changed object influenced accuracy in a related judgment task (Thornton and Fernandez-Duque 2000). The current studies explore whether these findings provide evidence for implicit change detection without explicit awareness or whether they could result from explicit processing. Methods: In Experiment 1, observers reported whether or not they believed a display change occurred and then rated their confidence in their response. In Experiment 2, on every trial, observers first performed an orientation judgment task and then noted whether or not they had seen a change. To replicate earlier results, the position of the target of the orientation judgment was spatially linked to the position of the changed item. In our new condition, this spatial link was disrupted. Results: As in earlier studies, observers were quicker to respond ‘same’ when there was no change than when there was a change. However, they were also quicker to respond when they were more confident, and these differences in confidence accounted for the response time differences when there was or was not a change. In Experiment 2, when the position of the changed item and the target of the perceptual judgment were spatially linked, the identity of the changed item affected the judgment. Yet, no influence remained when the spatial link was de-coupled, suggesting the effect may be due to an explicit search strategy. Conclusion: Our results question the existence of an implicit comparison process that allows for change detection in the absence of explicit processing.

Vision Sciences Society 2001

Presentation Abstracts