Abstracts2

How to correctly put the "subsequent" in subsequent search miss errors
Adamo, S. H., Cox, P. H., Kravitz, D. J., & Mitroff, S. R. (2019). How to correctly put the “subsequent” in subsequent search miss errors. Attention, Perception, & Psychophysics, 1-10.

Visual search, finding targets among distractors, is theoretically interesting and practically important as it involves many cognitive abilities and is vital for several critical industries (e.g., radiology, baggage screening). Unfortunately, search is especially error prone when more than one target is present in a display (a phenomenon termed the satisfaction of search effect or the subsequent search miss effect). The general effect is that observers are more likely to miss a second target if a first was already detected. Unpacking the underlying mechanisms requires two key aspects in analysis and design. First, to speak to the “subsequent” nature of the effect, the analyses must compare performance on single-target trials to performance for a second target in dual-target displays after a first has been found. Second, the design must include single-target displays that are matched in difficulty to each dual-target display to enable fair comparisons. However, it is not clear that prior research has met these two standards simultaneously. Work from academic radiology has primarily used designs with well-matched single- and dual-target trials, but most employed analyses that do not focus solely on performance after a first target has been detected. Work from cognitive psychology has generally performed the correct analyses, but relied on unmatched single- and dual-target trials, introducing a confound that could distort the results. In the current paper, we demonstrate the impact of this confound in empirical data and provide a roadmap for proper study design and analyses.

Evaluation of strategies to train visual search performance in professional populations
Kramer, M.S., Porfido, C.L., & Mitroff, S. R. (2019). Evaluation of strategies to train visual search performance in professional populations. Current Opinion in Psychology.

Visual search, the act of finding targets amongst distractors, is central to many professions with life-or-death implications including aviation security, radiology, lifeguarding, military, and more. As such, every effort should be taken to improve visual search performance. One potential path to improvement is to ensure that workforces are optimally trained. Broadly, there are three general components to train: (1) specific use of the machinery and user interface (i.e. 'knobology'), (2) target and distractor identification, and (3) search strategy. The current review considers the cognitive psychology aspects of these three components; each is evaluated in light of short-term and long-term training goals, as well as profession-specific constraints.

Satisfaction at last: Evidence for the "satisfaction" account for multiple-target search errors
Adamo, S. H., Cain, M. S., & Mitroff, S. R. (2018). Satisfaction at last: Evidence for the “satisfaction” account for multiple-target search errors. Proceedings SPIE: Medical Imaging, Image Perception, Observer Performance, and Technology Assessment. 105770A, doi.org/10.1117/12.2293692.

Multiple-target visual searches, where several targets may be present within a single search array, are susceptible to Subsequent Search Miss (SSM) errors—a reduction in second target detection after a first target has been found (an effect previously called Satisfaction of Search). SSM errors occur in critical search settings (e.g., radiology and airport security screening), creating concerns for public safety. To eradicate SSM errors it is vital to understand their cause(s), and the current study investigated a key proposed mechanism—searchers prematurely terminate their search after finding a first target. This proposed mechanism, termed the satisfaction account, was proposed over 50 years ago but there are no conclusive supporting data to date. “Satisfaction” has been typically assessed by comparing the total time spent on multiple-target trials to the time spent on single-target trials or by examining if search was immediately terminated after finding a first target. The current study investigated the satisfaction account by exploring variability in the time participants spent searching between finding a first target and self-terminating their search without finding a second target. This individual differences approach revealed that accuracy on a multiple-target search task related to how long participants searched after finding a first target. The relationship was highly significant, even when accounting for variation in participants’ attentional vigilance. This study provides evidence for the previously elusive satisfaction account and it adds to the growing understanding that SSM errors are a multifaceted problem.

Using cognitive psychology research to inform professional visual search operations
Biggs, A. T., Kramer, M. R., & Mitroff, S. R. (2018). Using cognitive psychology research to inform professional visual search operations. Journal of Applied Research in Memory and Cognition, 7(2), 189-198.

Visual search—locating target(s) among distractors—is a common practice that can range in difficulty from trivially easy to nearly impossible. Professional searches (e.g., airport security, radiology) typically are among the most complicated and challenging tasks, and also often among the most important. The current discussion examines empirical findings in the cognitive psychology literature that contribute to professional search operations, with an emphasis on airport security screening. Primarily, this article focuses on multiple ways to achieve optimal proficiency in security screenings, including personnel selection, training, and continuing assessments. Some of the existing best practices include using orthogonal visual search tasks as predictors of future performance (for selection), item-specific training (for expertise development), and annual competency tests (for continuing assessment). Future research opportunities are discussed, with one especially notable area for future research involving how individuals can potentially develop optimal scanning behaviors for professional search.

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. (2018). Mammography to tomosynthesis: examining the differences between two-dimensional and segmented-three-dimensional visual search. Cognitive Research: Principles and Implications, 3(1), 17.

BACKGROUND:
Radiological techniques for breast cancer detection are undergoing a massive technological shift-moving from mammography, a process that takes a two-dimensional (2D) image of breast tissue, to tomosynthesis, a technique that creates a segmented-three-dimensional (3D) image. There are distinct benefits of tomosynthesis over mammography with radiologists having fewer false positives and more accurate detections; yet there is a significant and meaningful disadvantage with tomosynthesis in that it takes longer to evaluate each patient. This added time can dramatically impact workflow and have negative attentional and cognitive impacts on interpretation of medical images. To better understand the nature of segmented-3D visual search and the implications for radiology, the current study looked to establish a new testing platform that could reliably examine differences between 2D and segmented-3D search.
RESULTS:
In Experiment 1, both professionals (radiology residents and certified radiologists) and non-professionals (undergraduate students) were found to have fewer false positives and were more accurate in segmented-3D displays, but at the cost of taking significantly longer in search. Experiment 2 tested a second group of non-professional participants, using a background that more closely resembled a mammogram, and replicated the results of Experiment 1-search was more accurate and there were fewer false alarms in segmented 3D displays but took more time.
CONCLUSION:
The results of Experiments 1 and 2 matched the performance patterns found in previous radiology studies and in the clinic, suggesting this novel experimental paradigm potentially provides a flexible and cost-effective tool that can be utilized with non-professional populations to inform relevant visual search performance. From an academic perspective, this paradigm holds promise for examining the nature of segmented-3D visual search.

Predicting airport screening officers' visual search competency with a rapid assessment
Mitroff, S. R., Ericson, J. M., & Sharpe, B. (2017). Predicting airport screening officers’ visual search competency with a rapid assessment. Human factors, 0018720817743886.

Objective: The study’s objective was to assess a new personnel selection and assessment tool for aviation security screeners. A mobile app was modified to create a tool, and the question was whether it could predict professional screeners’ on-job performance. Background: A variety of professions (airport security, radiology, the military, etc.) rely on visual search performance—being able to detect targets. Given the importance of such professions, it is necessary to maximize performance, and one means to do so is to select individuals who excel at visual search. A critical question is whether it is possible to predict search competency within a professional search environment. Method: Professional searchers from the USA Transportation Security Administration (TSA) completed a rapid assessment on a tablet-based X-ray simulator (XRAY Screener, derived from the mobile technology app Airport Scanner; Kedlin Company). The assessment contained 72 trials that were simulated X-ray images of bags. Participants searched for prohibited items and tapped on them with their finger. Results: Performance on the assessment significantly related to on-job performance measures for the TSA officers such that those who were better XRAY Screener performers were both more accurate and faster at the actual airport checkpoint. Conclusion: XRAY Screener successfully predicted on-job performance for professional aviation security officers. While questions remain about the underlying cognitive mechanisms, this quick assessment was found to significantly predict on-job success for a task that relies on visual search performance. Application: It may be possible to quickly assess an individual’s visual search competency, which could help organizations select new hires and assess their current workforce.

Using big data to solve real problems through academic and industry partnerships
Mitroff, S. R., & Sharpe, B. (2017). Using big data to solve real problems through academic and industry partnerships. Current Opinion in Behavioral Sciences, 18C, 91-96.

Big data has revolutionized a number of industries as it provides a powerful tool for asking and answering questions in novel ways. Academic researchers can join this trend and use immense and complex datasets to explore previously intractable questions. Yet, accessing and analyzing big data can be difficult. The goal of this chapter is to outline various benefits and challenges of using big data for academic purposes, and to provide thoughts on how to succeed. The primary suggestion is for academics to collaborate with appropriate industry partners to simultaneously achieve both theoretical and practical advances.

Emergency department crowding associated with differences in CXR interpretations between emergency physicians and radiologists
Chang, B.P., Cain, D., Mitroff S. R., (2017). Emergency department crowding associated with differences in CXR interpretations between emergency physicians and radiologists. The American Journal of Emergency Medicine, 35(5), 793-794

Emergency department (ED) crowding is a widespread challenge nationwide, with many EDs facing high ED patient volumes and increasing ambulance diversion, leading the Institute of Medicine to describe United States EDs as nearing the “breaking point” [1]. Emerging evidence has documented multiple negative outcomes associated with overcrowding, including increased walkout rates [2], delays in treatment during myocardial infarction [3], and increased mortality [4]. Other associated effects of overcrowding include poorer perceived clinician-patient communication [5], [6], and increased risk of posttraumatic stress symptoms following evaluation [7]. Past studies have also pointed to the potential for errors in clinical decision under times of stress and overcrowded clinical environments [8], [9] but little work has studied the association of crowding on clinical actions such as the interpretation of radiographic imaging in the ED.

A common mechanism for perceptual reversals in motion-induced blindness, the Troxler effect and perceptual filling-in
Devyatko, D., Appelbaum, L. G., & Mitroff, S. R. (2017). A Common Mechanism for Perceptual Reversals in Motion-Induced Blindness, the Troxler Effect, and Perceptual Filling-In. Perception, 46(1), 50-77

Several striking visual phenomena involve a physically present stimulus that alternates between being perceived and being ‘‘invisible.’’ For example, motion-induced blindness, the Troxler effect, and perceptual filling-in all consist of subjective alternations where an item repeatedly changes from being seen to unseen. In the present study, we explored whether these three specific visual phenomena share any commonalities in their alternation rates and patterns to better understand the mechanisms of each. Data from 69 individuals revealed moderate to strong correlations across the three phenomena for the number of perceptual disappearances and the accumulated duration of the disappearances. Importantly, these effects were not correlated with eye movement patterns (saccades) assessed through eye tracking, differences in motion sensitivity as indexed by dot coherence and speed perception thresholds, or simple reaction time abilities. Principal component analyses revealed a single component that explained 67% of the variance for the number of perceptual reversals and 60% for the accumulated duration of the disappearances. The temporal dynamics of illusory disappearances was also compared for each phenomenon, and normalized durations of disappearances were well fit by a gamma distribution with similar shape parameters for each phenomenon, suggesting that they may be driven by a single oscillatory mechanism.

An individual differences approach to multiple-target visual search errors: How search errors relate to different characteristics of attention
Adamo, S. H., Cain, M. S., & Mitroff, S. R. (2016). An individual differences approach to multiple-target visual search errors: How search errors relate to different characteristics of attention. Vision research.

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.

Fear generalization gradients in visuospatial attention
Dowd, E. W., Mitroff, S. R., & LaBar, K. S. (2016). Fear generalization gradients in visuospatial attention. Emotion.

Fear learning can be adaptively advantageous, but only if the learning is integrated with higher-order cognitive processes that impact goal-directed behaviors. Recent work has demonstrated generalization (i.e., transfer) of conditioned fear across perceptual dimensions and conceptual categories, but it is not clear how fear generalization influences other cognitive processes. The current study investigated how associative fear learning impacts higher-order visuospatial attention, specifically in terms of attentional bias toward generalized threats (i.e., the heightened assessment of potentially dangerous stimuli). We combined discriminative fear conditioning of color stimuli with a subsequent visual search task, in which targets and distractors were presented inside colored circles that varied in perceptual similarity to the fear-conditioned color. Skin conductance responses validated the fear-conditioning manipulation. Search response times indicated that attention was preferentially deployed not just to the specific fear- conditioned color, but also to similar colors that were never paired with the aversive shock. Furthermore, this attentional bias decreased continuously and symmetrically from the fear-conditioned value along the color spectrum, indicating a generalization gradient based on perceptual similarity. These results support functional accounts of fear learning that promote broad, defensive generalization of attentional bias toward threat.

Visual search: You are who you are (+ a learning curve)
Ericson, J. M., Kravitz, D. J., & Mitroff, S. R. (2017). Visual search: You are who you are (+ a learning curve). Perception, 0(0), 1-8.

Not everyone is equally well suited for every endeavor—individuals differ in their strengths and weaknesses, which makes some people better at performing some tasks than others. As such, it might be possible to predict individuals’ peak competence (i.e., ultimate level of success) on a given task based on their early performance in that task. The current study leveraged ‘‘big data’’ from the mobile game, Airport Scanner (Kedlin Company), to assess the possibility of predicting individuals’ ultimate visual search competency using the minimum possible unit of data: response time on a single visual search trial. Those who started out poorly were likely to stay relatively poor and those who started out strong were likely to remain top performers. This effect was apparent at the level of a single trial (in fact, the first trial), making it possible to use raw response time to predict later levels of success.

Who should be searching? Differences in personality can affect visual search accuracy
Biggs, A. T., Clark, K., & Mitroff, S. R. (2017). Who should be searching? Differences in personality can affect visual search accuracy. Personality and Individual Differences, 116, 353-358.

Visual search is an everyday task conducted in a wide variety of contexts. Some searches are mundane, such as finding a beverage in the refrigerator, and some have life-or-death consequences, such as finding improvised ex- plosives at a security checkpoint or within a combat zone. Prior work has shown numerous influences on search, including “bottom-up” (physical stimulus attributes) and “top-down” factors (task-relevant or goal-driven as- pects). Recent work has begun to focus on “observer-specific” factors, examining how searchers' attributes might influence search performance. A logical extension involves exploring whether some individuals are better suited to conduct visual searches than other individuals. The current study examined whether certain personality characteristics relate to visual search performance in a large sample of professional searchers employed by the U.S. Transportation Security Administration. Of the “big five” personality traits (neuroticism, extroversion, open- ness, agreeableness, and conscientiousness), only conscientiousness significantly correlated with visual search accuracy. Both early-career and experienced professional searchers demonstrated a significant relationship be- tween conscientiousness scores and accuracy on a simple visual search task. These findings validate the notion that searchers' attributes impact their visual search performance and suggest that personality assessments might prove useful for hiring and selection decisions regarding professional tasks that incorporate visual search.

Sensorimotor learning in a computerized athletic training battery
Krasich, K., Ramger, B., Holton, L., Wang, L., Mitroff, S. R., & Appelbaum, L. G. (2016). Sensorimotor learning in a computerized athletic training battery. Journal of Motor Behavior, 48(5), 401-412.

Sensorimotor abilities are crucial for performance in athletic, military, and other occupational activities, and there is great interest in understanding learning in these skills. Here, behavioral performance was measured over three days as twenty- seven participants practiced multiple sessions on the Nike SPARQ Sensory Station (Nike, Inc., Beaverton, Oregon), a computerized visual and motor assessment battery. Wrist-worn actigraphy was recorded to monitor sleep–wake cycles. Significant learning was observed in tasks with high visuomotor control demands but not in tasks of visual sensitivity. Learning was primarily linear, with up to 60% improvement, but did not relate to sleep quality in this nor- mal-sleeping population. These results demonstrate differences in the rate and capacity for learning across perceptual and motor domains, indicating potential targets for sensorimotor training interventions.

Targets need their own space: Effects of clutter on multiple-target visual search
Adamo, S. H., Cain, M. S., & Mitroff, S. R. (2015). Targets need their own space: Effects of clutter on multiple-target visual search. Perception, 44(10), 1203-1214.

Visual search is an essential task for many lifesaving professions; airport security personnel search baggage X-ray images for dangerous items and radiologists examine radiographs for tumors. Accuracy is critical for such searches; however, there are potentially negative influences that can affect performance; for example, the displays can be cluttered and can contain multiple targets. Previous research has demonstrated that clutter can hurt search performance and a second target is less likely to be detected in a multiple-target search after a first target has been found, which raises a concern—how does clutter affect multiple-target search performance? The current study explored clutter in a multiple-target search paradigm, where there could be one or two targets present, and targets appeared in varying levels of clutter. There was a significant interaction between clutter and target number: Increasing levels of clutter did not affect single-target detection but did reduce detection of a second target. Multiple-target search accuracy is known to be sensitive to contextual influences, and the current results reveal a specific effect wherein clutter disproportionally affected multiple-target search accuracy. These results suggest that the detection and processing of a first target might enhance the masking effects of clutter around a second target.

Multiple-target visual search errors: Overview and implications for airport security
Mitroff, S. R., Biggs, A. T., & Cain, M. S. (2015). Multiple-target visual search errors: Overview and implications for airport security. Policy Insights from the Behavioral and Brain Sciences, 2(1), 121-128.

Visual search—the ability to locate visual targets among distractors—is a fundamental part of professional performance for many careers, including radiology, airport security screening, cytology, lifeguarding, and more. Successful execution of visual search in these settings is critically important because the consequences of a missed target can be horrific. Unfortunately, many of these professions place high demands on the people performing the searches, and either the task or the environment (or both) could lead to significant errors. One known source of error that exists across many fields is “multiple-target visual search” errors—a target is less likely to be detected if another target was already found in the same search than if the target was the only one present. These errors have proven to be stubborn and not easily eliminated. This article offers a brief overview of the existing research on multiple-target visual search errors and discusses possible policy implications of the errors for airport security screening. The policy suggestions are based on empirical research, with the hope of providing food for thought on using scientific data and theory to improve performance. Specifically, three policy suggestions are raised: shift screening to a remote location away from the checkpoint, reduce the number of prohibited items to lessen the searchers’ cognitive burden, and emphasize search consistency in the training process. Note that the focus here is on airport security screening, as this is a domain most readers can relate to, but the suggestions can equally apply to many search environments.

Cognitive training can reduce civilian casualties in a simulated shooting environment
Biggs, A. T., Cain, M. S., Mitroff, S. R. (2015). Cognitive training can reduce civilian casualties in a simulated shooting environment. Psychological Science, 26(8), 1164-1176.

Shooting a firearm involves a complex series of cognitive abilities. For example, locating an item or a person of interest requires visual search, and firing the weapon (or withholding a trigger squeeze) involves response execution (or inhibition). The present study used a simulated shooting environment to establish a relationship between a particular cognitive ability and a critical shooting error—response inhibition and firing on civilians, respectively. Individual- difference measures demonstrated, perhaps counterintuitively, that simulated civilian casualties were not related to motor impulsivity (i.e., an itchy trigger finger) but rather to an individual’s cognitive ability to withhold an already initiated response (i.e., an itchy brain). Furthermore, active-response-inhibition training reduced simulated civilian casualties, which revealed a causal relationship. This study therefore illustrates the potential of using cognitive training to possibly improve shooting performance, which might ultimately provide insight for military and law-enforcement personnel.

Mo’ money, mo’ problems: Monetary motivation can exacerbate the attentional blink
Biggs, A. T., Adamo, S. H., & Mitroff, S. R. (2015). Mo’ money, mo’ problems: Monetary motivation can exacerbate the attentional blink. Perception, 44(4), 410-422.

The attentional blink (AB) is a compelling psychological phenomenon wherein observers are less likely to identify a second target (T2) when it appears approximately 200 ms after a first target (T1) in a rapidly presented stream of items. The present investigation examined how monetary motivation could impact the AB when participants were differentially motivated to identify T1 versus T2. Participants completed one of three conditions where the only difference across conditions was a motivational manipulation: a standard AB task (control condition), a motivated condition with T1 worth double the points of T2, or a motivated condition with T1 worth half the points of T2 (points in the motivated conditions were linked to a possible monetary bonus). Motivation had an expected influence on overall performance as both motivated conditions had higher overall T1 accuracy relative to the control condition. More specific to the question at hand, the AB was exacerbated (ie T2 performance was worse shortly after T1) when T1 was worth more than T2. This finding suggests that participants overallocated attentional resources to T1 processing at the expense of T2 processing, and it supports current theories of the AB.

Improvement in visual search with practice: Mapping learning-related changes in neurocognitive stages of processing
Clark, K., Appelbaum, L. G., van de berg, B., Mitroff, S. R., & Woldorff, M. G. (2015). Improvement in visual search with practice: Mapping learning-related changes in neurocognitive stages of processing. Journal of Neuroscience, 35(13): 5351-5359.

Practice can improve performance on visual search tasks; the neural mechanisms underlying such improvements, however, are not clear. Response time typically shortens with practice, but which components of the stimulus–response processing chain facilitate this behav- ioral change? Improved search performance could result from enhancements in various cognitive processing stages, including (1) sensory processing, (2) attentional allocation, (3) target discrimination, (4) motor-response preparation, and/or (5) response execution. We measured event-related potentials (ERPs) as human participants completed a five-day visual-search protocol in which they reported the orientation of a color popout target within an array of ellipses. We assessed changes in behavioral performance and in ERP compo- nents associated with various stages of processing. After practice, response time decreased in all participants (while accuracy remained consistent), and electrophysiological measures revealed modulation of several ERP components. First, amplitudes of the early sensory- evoked N1 component at 150 ms increased bilaterally, indicating enhanced visual sensory processing of the array. Second, the negative- polarity posterior– contralateral component (N2pc, 170 –250 ms) was earlier and larger, demonstrating enhanced attentional orienting. Third, the amplitude of the sustained posterior contralateral negativity component (SPCN, 300 – 400 ms) decreased, indicating facilitated target discrimination. Finally, faster motor-response preparation and execution were observed after practice, as indicated by latency changes in both the stimulus-locked and response-locked lateralized readiness potentials (LRPs). These electrophysiological results delineate the functional plasticity in key mechanisms underlying visual search with high temporal resolution and illustrate how practice influences various cognitive and neural processing stages leading to enhanced behavioral performance.

Attentional guidance by working memory differs by paradigm: An individual-differences approach
Dowd, E. W., Kiyonaga, A., Egner, T., & Mitroff, S. R. (2015). Attentional guidance by working memory differs by paradigm: An individual-differences approach. Attention, Perception, & Psychophysics, 77, 704- 712.

Abstract The contents of working memory (WM) have been repeatedly found to guide the allocation of visual attention; in a dual-task paradigm that combines WM and visual search, actively holding an item in WM biases visual attention towards memory-matching items during search (e.g., Soto et al., Jour- nal of Experimental Psychology: Human Perception and Performance, 31(2), 248-261, 2005). A key debate is whether such memory-based attentional guidance is automatic or under strategic control. Generally, two distinct task paradigms have been employed to assess memory-based guidance, one demonstrating that attention is involuntarily captured by memory- matching stimuli even at a cost to search performance (Soto et al., 2005), and one demonstrating that participants can strategically avoid memory-matching distractors to facilitate search performance (Woodman & Luck, Journal of Experimental Psychology: Human Perception and Performance, 33(2), 363-377, 2007). The current study utilized an individual- differences approach to examine why the different paradigms—which presumably tap into the same attentional construct might support contrasting interpretations. Participants completed a battery of cognitive tasks, including two types of attentional guidance paradigms (see Soto et al., 2005; Wood- man & Luck, 2007), a visual WM task, and an operation span task, as well as attention-related self-report assessments. Performance on the two attentional guidance paradigms did not correlate. Subsequent exploratory regression analyses revealed that memory-based guidance in each task was differentially predict- ed by visual WM capacity for one paradigm, and by attention- related assessment scores for the other paradigm. The current results suggest that these two paradigms—which have previously produced contrasting patterns of performance— may probe distinct aspects of attentional guidance.

Mapping the structure of perceptual and visual-motor abilities in healthy young adults
Wang, L., Krasich, K., Bel-Bahar, T., Hughes, L., Mitroff, S. R., & Appelbaum, L. G. (2015). Mapping the structure of perceptual and visual-motor abilities in healthy young adults. Acta Psychologica, 157, 74-84.

The ability to quickly detect and respond to visual stimuli in the environment is critical to many human activities. While such perceptual and visual–motor skills are important in a myriad of contexts, considerable variability exists between individuals in these abilities. To better understand the sources of this variability, we assessed per- ceptual and visual–motor skills in a large sample of 230 healthy individuals via the Nike SPARQ Sensory Station, and compared variability in their behavioral performance to demographic, state, sleep and consumption charac- teristics. Dimension reduction and regression analyses indicated three underlying factors: Visual–Motor Control, Visual Sensitivity, and Eye Quickness, which accounted for roughly half of the overall population variance in performance on this battery. Inter-individual variability in Visual–Motor Control was correlated with gender and circadian patters such that performance on this factor was better for males and for those who had been awake for a longer period of time before assessment. The current findings indicate that abilities involving coor- dinated hand movements in response to stimuli are subject to greater individual variability, while visual sensitiv- ity and occulomotor control are largely stable across individuals.

Examining perceptual and conceptual set biases in multiple-target visual search
Biggs, A. T., Adamo, S. H., Dowd, E. W., & Mitroff, S. R. (2015). Examining perceptual and conceptual set biases in multiple-target visual search. Attention, Perception, & Psychophysics, 77, 844-855.

Abstract Visual search is a common practice conducted countless times every day, and one important aspect of visual search is that multiple targets can appear in a single search array. For example, an X-ray image of airport luggage could contain both a water bottle and a gun. Searchers are more likely to miss additional targets after locating a first target in multiple-target searches, which presents a potential problem: If airport security officers were to find a water bottle, would they then be more likely to miss a gun? One hypothetical cause of multiple-target search errors is that searchers become biased to detect additional targets that are similar to a found target, and therefore become less likely to find additional tar- gets that are dissimilar to the first target. This particular hy- pothesis has received theoretical, but little empirical, support. In the present study, we tested the bounds of this idea by utilizing “big data” obtained from the mobile application Airport Scanner. Multiple-target search errors were substan- tially reduced when the two targets were identical, suggesting that the first-found target did indeed create biases during sub- sequent search. Further analyses delineated the nature of the biases, revealing both a perceptual set bias (i.e., a bias to find additional targets with features similar to those of the first- found target) and a conceptual set bias (i.e., a bias to find additional targets with a conceptual relationship to the first- found target). These biases are discussed in terms of the im- plications for visual-search theories and applications for pro- fessional visual searchers.

What can 1 billion trials tell us about visual search?
Mitroff, S. R., Biggs, A. T., Adamo, S. H., Dowd, E. W., Winkle, J., & Clark, K. (2015). What can 1 billion trials tell us about visual search? Journal of Experimental Psychology: Human Perception & Performance, 41(1), 1-5.

Mobile technology (e.g., smartphones and tablets) has provided psychologists with a wonderful oppor- tunity: through careful design and implementation, mobile applications can be used to crowd source data collection. By garnering massive amounts of data from a wide variety of individuals, it is possible to explore psychological questions that have, to date, been out of reach. Here we discuss 2 examples of how data from the mobile game Airport Scanner (Kedlin Co., http://www.airportscannergame.com) can be used to address questions about the nature of visual search that pose intractable problems for laboratory- based research. Airport Scanner is a successful mobile game with millions of unique users and billions of individual trials, which allows for examining nuanced visual search questions. The goals of the current Observation Report were to highlight the growing opportunity that mobile technology affords psycho- logical research and to provide an example roadmap of how to successfully collect usable data.

Improving the efficacy of security screening tasks: A review of visual search challenges and ways to mitigate their adverse effects
Biggs, A. T., & Mitroff, S. R. (2014). Improving the efficacy of security screening tasks: A review of visual search challenges and ways to mitigate their adverse effects. Applied Cognitive Psychology, 29(1), 142-148.

Security checkpoints are used to keep potentially dangerous items and individuals out of secure areas. Although technological advances can enhance security efficacy through both accuracy and speed, ultimate success or failure is largely determined by human performance. As such, it is necessary to minimize any shortcomings that stem from the limits of human cognitive abilities. Cognitive performance can be influenced by numerous factors, including those imposed by the search task (e.g., the number of prohibited items) and the basic abilities of the searchers themselves (e.g., competency and experience). Here, we review and discuss four specific challenges of the task itself that can negatively affect the accuracy of a security screening: target visibility, an unknown target set, the possible presence of multiple targets, and low target prevalence. For each, we present the challenge faced and the potential significance of the challenge and then offer possible solutions on the basis of the existing literature.

Differences in multiple-target visual search performance between non-professional and professional searchers due to decision-making criteria
Biggs, A. T., & Mitroff, S. R. (2014). Differences in multiple-target visual search performance between non-professional and professional searchers due to decision-making criteria. British Journal of Psychology.

Professional visual searches, such as those conducted by airport security personnel, often demand highly accurate performance. As many factors can hinder accuracy, it is critical to understand the potential influences. Here, we examined how explicit decision-making criteria might affect multiple-target search performance. Non-professional searchers (college undergraduates) and professional searchers (airport security officers) classified trials as ‘safe’ or ‘dangerous’, in one of two conditions. Those in the ‘one = dangerous’ condition classified trials as dangerous if they found one or two targets, and those in the ‘one = safe’ condition only classified trials as dangerous if they found two targets. The data suggest an important role of context that may be mediated by experience; non-professional searchers were more likely to miss a second target in the one = dangerous condition (i.e., when finding a second found target did not change the classification), whereas professional searchers were more likely to miss a second in the one = safe condition.

Rare, but obviously there: Effects of target frequency and salience on visual search accuracy
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.

Accuracy can be extremely important for many visual search tasks. However, numerous factors work to under- mine successful search. Several negative influences on search have been well studied, yet one potentially influ- ential factor has gone almost entirely unexplored--namely, how is search performance affected by the likelihood that a specific target might appear? A recent study demonstrated that when specific targets appear in- frequently (i.e., once in every thousand trials) they were, on average, not often found. Even so, some infrequently appearing targets were actually found quite often, suggesting that the targets' frequency is not the only factor at play. Here, we investigated whether salience (i.e., the extent to which an item stands out during search) could explain why some infrequent targets are easily found whereas others are almost never found. Using the mobile application Airport Scanner, we assessed how individual target frequency and salience interacted in a visual search task that included a wide array of targets and millions of trials. Target frequency and salience were both significant predictors of search accuracy, although target frequency explained more of the accuracy variance. Fur- ther, when examining only the rarest target items (those that appeared on less than 0.15% of all trials), there was a significant relationship between salience and accuracy such that less salient items were less likely to be found. Beyond implications for search theory, these data suggest significant vulnerability for real-world searches that involve targets that are both infrequent and hard-to-spot.

A little bit of history repeating: Splitting up multiple-target visual searches decreases second-target miss errors
Cain, M. S., Biggs, A. T., Darling, E. F., & Mitroff, S. R. (2014). A little bit of history repeating: Splitting up multiple-target visual searches decreases second-target miss errors. Journal of Experimental Psychology: Applied, 20(2), 112-125.

Visual searches with several targets in a display have been shown to be particularly prone to miss errors in both academic laboratory searches and professional searches such as radiology and baggage screening. Specifically, finding 1 target in a display can reduce the likelihood of detecting additional targets. This phenomenon was originally referred to as “satisfaction of search,” but is referred to here as “subsequent search misses” (SSMs). SSM errors have been linked to a variety of causes, and recent evidence supports a working memory deficit wherein finding a target consumes working memory resources that would otherwise aid subsequent search for additional targets (Cain & Mitroff, 2013). The current study demonstrated that dividing 1 multiple-target search into several single-target searches, separated by three to five unrelated trials, effectively freed the working memory resources used by the found target and eliminated SSM errors. This effect was demonstrated with both university community participants and with professional visual searchers from the Transportation Security Administration, suggesting it may be a generally applicable technique for improving multiple-target visual search accuracy.

Context Matters: The structure of task goals affects accuracy in multiple-target visual search
Clark, K., Cain, M. S., Adcock, R. A., & Mitroff, S. R. (2014). Context Matters: The structure of task goals affects accuracy in multiple-target visual search. Applied Ergonomics, 45(3), 528-533.

Career visual searchers such as radiologists and airport security screeners strive to conduct accurate visual searches, but despite extensive training, errors still occur. A key difference between searches in radiology and airport security is the structure of the search task: Radiologists typically scan a certain number of medical images (fixed objective), and airport security screeners typically search X-rays for a specified time period (fixed duration). Might these structural differences affect accuracy? We compared performance on a search task administered either under constraints that approximated radiology or airport security. Some displays con- tained more than one target because the presence of multiple targets is an established source of errors for career searchers, and accuracy for additional targets tends to be especially sensitive to contextual conditions. Results indicate that participants searching within the fixed objective framework produced more multiple- target search errors; thus, adopting a fixed duration framework could improve accuracy for career searchers.

The Ultra-Rare-Item effect: Visual search for exceedingly rare items is highly susceptible to error
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.

Accuracy is paramount in radiology and security screening, yet many factors undermine success. Target prevalence is a particularly worrisome factor, as targets are rarely present (e.g., the cancer rate in mammography is ~0.5%), and low target prevalence has been linked to increased search errors. More troubling is the fact that specific target types can have extraordinarily low frequency rates (e.g., architectural distortions in mammography—a specific marker of potential cancer—appear in fewer than 0.05% of cases). By assessing search performance across millions of trials from the Airport Scanner smartphone application, we demonstrated that the detection of ultra-rare items was disturbingly poor. A logarithmic relationship between target detection and target frequency (adjusted R2 = .92) revealed that ultra- rare items had catastrophically low detection rates relative to targets with higher frequencies. Extraordinarily low search performance for these extraordinarily rare targets—what we term the ultra-rare-item effect—is troubling given that radiological and security-screening searches are primarily ultra-rare-item searches.

Different predictors of multiple-target search accuracy between nonprofessional and professional visual searchers
Biggs, A. T., & Mitroff, S. R. (2014). Different predictors of multiple-target search accuracy between nonprofessional and professional visual searchers. Quarterly Journal of Experimental Psychology, 67(7), 1335- 1348.

Visual search, locating target items among distractors, underlies daily activities ranging from critical tasks (e.g., looking for dangerous objects during security screening) to commonplace ones (e.g., finding your friends in a crowded bar). Both professional and nonprofessional individuals conduct visual searches, and the present investigation is aimed at understanding how they perform similarly and differently. We administered a multiple-target visual search task to both professional (airport security officers) and nonprofessional participants (members of the Duke University community) to determine how search abilities differ between these populations and what factors might predict accuracy. There were minimal overall accuracy differences, although the professionals were generally slower to respond. However, the factors that predicted accuracy varied drastically between groups; variability in search consistency—how similarly an individual searched from trial to trial in terms of speed—best explained accuracy for professional searchers (more consistent professionals were more accurate), whereas search speed—how long an individual took to complete a search when no targets were present—best explained accuracy for nonprofessional searchers (slower nonprofessionals were more accurate). These findings suggest that professional searchers may utilize different search strategies from those of nonprofessionals, and that search consistency, in particular, may provide a valuable tool for enhancing professional search accuracy.

Enhancing ice hockey skills through stroboscopic visual training—A pilot study
Mitroff, S. R., Friesen, P., Bennett, D., Yoo, H., & Reichow, A. (2013). Enhancing ice hockey skills through stroboscopic visual training—A pilot study. Athletic Training & Sports Health Care, 5, 261-264.

Recent research has suggested that a new sport training tool may enhance vision, attention, and response timing. The tool, stroboscopic eyewear, includes lenses that alternate between transparent and opaque states to produce stroboscopic visual conditions. Previous research has demonstrated that strobo- scopic training can improve visual abilities, but can strobo- scopic training affect sport performance directly? The current pilot study explored this question by assessing athletic skill in professional ice hockey players. Participants trained either with stroboscopic eyewear (strobe group) or with no eyewear (con- trol group). The strobe group averaged an 18% improvement in on-ice skill performance from pretraining to posttraining, whereas the control group’s performance did not improve. The current results demonstrate improvement in the athletic skill of professional athletes with training that added one new com- ponent—wearing stroboscopic eyewear—to their normal rou- tines.

Self-induced attentional blink: A cause of errors in multiple-target search
Adamo, S. H., Cain, M. S., & Mitroff, S. R. (2013). Self-induced attentional blink: A cause of errors in multiple-target search. Psychological Science, 24(12), 2569-2574.

Satisfaction of search (which we refer to as subsequent search misses)—a decrease in accuracy at detecting a second target after a first target has been found in a visual search—underlies real-world search errors (e.g., tumors may be missed in an X-ray if another tumor already has been found), but little is known about this phenomenon’s cognitive underpinnings. In the present study, we examined subsequent search misses in terms of another, more extensively studied phenomenon: the attentional blink, a decrease in accuracy when a second target appears 200 to 500 ms after a first target is detected in a temporal stream. Participants searched for T-shaped targets among L-shaped distractors in a spatial visual search, and despite large methodological differences between self-paced spatial visual searches and attentional blink tasks, an attentional-blink-like effect accounted for subsequent-search-miss errors. This finding provides evidence that accuracy is negatively affected shortly after a first target is fixated in a self-paced, self-guided visual search.

A taxonomy of multiple-target search errors
Cain, M. S., Adamo, S. H., & Mitroff, S. R. (2013). A taxonomy of multiple-target search errors. Visual Cognition, 21(7), 899-921.

Multiple-target visual searches are especially error prone; once one target is found, additional targets are likely to be missed. This phenomenon, often called satisfaction of search (which we refer to here as subsequent search misses; SSMs), is well known in radiology, despite no existing consensus about the underlying cause(s). Taking a cognitive laboratory approach, we propose that there are multiple causes of SSMs and present a taxonomy of SSMs based on searchers’ eye movements during a multiple-target search task, including both previously identified and novel sources of SSMs. The types and distributions of SSMs revealed effects of working memory load, search strategy, and additional causal factors, suggesting that there is no single cause of SSMs. A multifaceted approach is likely needed to understand the psychological causes of SSMs and then to mitigate them in applied settings such as radiology and baggage screening.

Enhanced facial symmetry assessment in orthodontists
Jackson, T. H., Clark, K., & Mitroff, S. R. (2013). Enhanced facial symmetry assessment in orthodontists. Visual Cognition, 21(7), 838-852.

Assessing facial symmetry is an evolutionarily important process, which suggests that individual differences in this ability should exist. As existing data are inconclusive, the current study explored whether a group trained in facial symmetry assessment, orthodontists, possessed enhanced abilities. Symmetry assessment was measured using face and nonface stimuli among orthodontic residents and two control groups: university participants with no symmetry training and airport security luggage screeners, a group previously shown to possess expert visual search skills unrelated to facial symmetry. Orthodontic residents were more accurate at assessing symmetry in both upright and inverted faces compared to both control groups, but not for nonface stimuli. These differences are not likely due to motivational biases or a speed–accuracy tradeoff— orthodontic residents were slower than the university participants but not the security screeners. Understanding such individual differences in facial symmetry assessment may inform the perception of facial attractiveness.

Action video game playing is associated with improved visual sensitivity, but not alterations in visual sensory memory
Appelbaum, L. G., Cain, M. S., Darling, E. F., & Mitroff, S. R. (2013). Action video game playing is associated with improved visual sensitivity, but not alterations in visual sensory memory. Attention, Perception, & Psychophysics, 75(6), 1161-1167.

Action video game playing has been experimentally linked to a number of perceptual and cognitive improvements. These benefits are captured through a wide range of psycho- metric tasks and have led to the proposition that action video game experience may promote the ability to extract statistical evidence from sensory stimuli. Such an advantage could arise from a number of possible mechanisms: improvements in visual sensitivity, enhancements in the capacity or duration for which information is retained in visual memory, or higher-level strate- gic use of information for decision making. The present study measured the capacity and time course of visual sensory mem- ory using a partial report performance task as a means to distinguish between these three possible mechanisms. Sensitivity measures and parameter estimates that describe sen- sory memory capacity and the rate of memory decay were compared between individuals who reported high evels and low levels of action video game experience. Our results revealed a uniform increase in partial report accuracy at all stimulus-to- cue delays for action video game players but no difference in the rate or time course of the memory decay. The present findings suggest that action video game playing may be related to enhancements in the initial sensitivity to visual stimuli, but not to a greater retention of information in iconic memory buffers.

Assessing visual search performance differences between Transportation Security Administration Officers and non-professional visual searchers
Biggs, A. T., Cain, M. S., Clark, K., Darling, E. F., & Mitroff, S. R. (2013). Assessing visual search performance differences between Transportation Security Administration Officers and non-professional visual searchers. Visual Cognition, 21(3), 330-352.

Some visual searches depend upon accuracy (e.g., radiology, airport security screening), and it is important for both theoretical and applied reasons to understand what factors best predict performance. The current study administered a visual search task to both professional (Transportation Security Administration Officers) and nonprofessional (members of Duke University) searchers to examine group differences in which factors predict accuracy. Search speed*time taken to terminate search*was the primary predictor for nonprofessional searchers (accounting for 59% of their accuracy variability) and for the least experienced professional searchers (37% of variability). In contrast, consistency*how similarly (in terms of search speed) an individual spent searching from trial to trial*was the primary predictor for the most experienced professional visual searchers (39% of variability). These results inform cognitive theory by illuminating factors that differentially affect search performance between participants, and real-world issues by identifying search behaviours (consistency in particular) important to experi- enced professional searchers.

Attentional guidance by working memory overrides saliency cues in visual search
Dowd, E. W., & Mitroff, S. R. (2013). Attentional guidance by working memory overrides saliency cues in visual search. Journal of Experimental Psychology: Human Perception & Performance, 39(6), 1786- 1796.

Many factors influence visual search, including how much targets stand out (i.e., their visual salience) and whether they are currently relevant (i.e., Are they in working memory?). Although these are two known influences on search performance, it is unclear how they interact to guide attention. The present study explored this interplay by having participants hold an item in memory for a subsequent test while simultaneously conducting a multiple-target visual search. Importantly, the memory item could match one or neither of two targets from the search. In Experiment 1, when the memory item did not match either target, participants found a high-salience target first, demonstrating a baseline salience effect. This effect was exaggerated when a high-salience target was in working memory and completely reversed when a low-salience target was in memory, demonstrating a powerful influence of working memory guidance. Experiment 2 amplified the salience effect by including very high-salience, “pop-out”-like targets. Yet this salience effect was still attenuated when the memory item matched a less salient target. Experiment 3 confirmed these were memory-based effects and not priming. Collectively, these findings illustrate the influential role of working memory in guiding visual attention, even in the face of competing bottom-up salience cues.

Memory for found targets interferes with subsequent performance in multiple-target visual search
Cain, M. S., & Mitroff, S. R. (2013). Memory for found targets interferes with subsequent performance in multiple-target visual search. Journal of Experimental Psychology: Human Perception & Performance, 39(5), 1398-1408.

Multiple-target visual searches—when more than 1 target can appear in a given search display—are commonplace in radiology, airport security screening, and the military. Whereas 1 target is often found accurately, additional targets are more likely to be missed in multiple-target searches. To better understand this decrement in 2nd-target detection, here we examined 2 potential forms of interference that can arise from finding a 1st target: interference from the perceptual salience of the 1st target (a now highly relevant distractor in a known location) and interference from a newly created memory representation for the 1st target. Here, we found that removing found targets from the display or making them salient and easily segregated color singletons improved subsequent search accuracy. However, replacing found targets with random distractor items did not improve subsequent search accuracy. Removing and highlighting found targets likely reduced both a target’s visual salience and its memory load, whereas replacing a target removed its visual salience but not its representation in memory. Collectively, the current experiments suggest that the working memory load of a found target has a larger effect on subsequent search accuracy than does its perceptual salience.

Different predictors of multiple-target search accuracy between nonprofessional and professional visual searchers
Biggs, A. T., & Mitroff, S. R. (2014). Different predictors of multiple-target search accuracy between nonprofessional and professional visual searchers. The Quarterly Journal of Experimental Psychology, 67(7), 1335-1348.

Visual search, locating target items among distractors, underlies daily activities ranging from critical tasks (e.g., looking for dangerous objects during security screening) to commonplace ones (e.g., finding your friends in a crowded bar). Both professional and nonprofessional individuals conduct visual searches, and the present investigation is aimed at understanding how they perform similarly and differently. We administered a multiple-target visual search task to both professional (airport secur- ity officers) and nonprofessional participants (members of the Duke University community) to deter- mine how search abilities differ between these populations and what factors might predict accuracy. There were minimal overall accuracy differences, although the professionals were generally slower to respond. However, the factors that predicted accuracy varied drastically between groups; variability in search consistency--how similarly an individual searched from trial to trial in terms of speed--best explained accuracy for professional searchers (more consistent professionals were more accurate), whereas search speed--how long an individual took to complete a search when no targets were present--best explained accuracy for nonprofessional searchers (slower nonprofessionals were more accurate). These findings suggest that professional searchers may utilize different search strategies from those of nonprofessionals, and that search consistency, in particular, may provide a valuable tool for enhancing professional search accuracy.

Stroboscopic training enhances anticipatory timing
Smith, T. Q., & Mitroff, S. R. (2012). Stroboscopic training enhances anticipatory timing. International Journal of Exercise Science, 5(4), 344-353.

The dynamic aspects of sports often place heavy demands on visual processing. As such, an important goal for sports training should be to enhance visual abilities. Recent research has suggested that training in a stroboscopic environment, where visual experiences alternate between visible and obscured, may provide a means of improving attentional and visual abilities. The current study explored whether stroboscopic training could impact anticipatory timing the ability to predict where a moving stimulus will be at a specific point in time. Anticipatory timing is a critical skill for both sports and non-sports activities, and thus finding training improvements could have broad impacts. Participants completed a pre-training assessment that used a Bassin Anticipation Timer to measure their abilities to accurately predict the timing of a moving visual stimulus. Immediately after this initial assessment, the participants completed training trials, but in one of two conditions. Those in the Control condition proceeded as before with no change. Those in the Strobe condition completed the training trials while wearing specialized eyewear that had lenses that alternated between transparent and opaque (rate of 100ms visible to 150ms opaque). Post- training assessments were administered immediately after training, 10-minutes after training, and 10-days after training. Compared to the Control group, the Strobe group was significantly more accurate immediately after training, was more likely to respond early than to respond late immediately after training and 10 minutes later, and was more consistent in their timing estimates immediately after training and 10 minutes later.

Links between multisensory processing and autism
Donohue, S. E., Darling, E. F., Mitroff, S. R. (2012). Links between multisensory processing and autism. Experimental Brain Research, 222, 377-387.

Abstract Autism spectrum disorder is typically associ- ated with social deficits and is often specifically linked to difficulty with processing faces and other socially relevant stimuli. Emerging research has suggested that children with autism might also have deficits in basic perceptual abilities including multisensory processing (e.g., simultaneously processing visual and auditory inputs). The current study examined the relationship between multisensory temporal processing (assessed via a simultaneity judgment task wherein participants were to report whether a visual stim- ulus and an auditory stimulus occurred at the same time or at different times) and self-reported symptoms of autism (assessed via the Autism Spectrum Quotient question- naire). Data from over 100 healthy adults revealed a rela- tionship between these two factors as multisensory timing perception correlated with symptoms of autism. Specifi- cally, a stronger bias to perceive auditory stimuli occurring before visual stimuli as simultaneous was associated with greater levels of autistic symptoms. Additional data and analyses confirm that this relationship is specific to multi- sensory processing and symptoms of autism. These results provide insight into the nature of multisensory processing while also revealing a continuum over which perceptual abilities correlate with symptoms of autism and that this continuum is not just specific to clinical populations but is present within the general population.

A Bayesian optimal foraging model of human visual search
Cain, M. S., Vul, E., Clark, K., & Mitroff, S. R. (2012). A Bayesian optimal foraging model of human visual search. Psychological Science, 23, 1047-1054.

Real-world visual searches often contain a variable and unknown number of targets. Such searches present difficult metacognitive challenges, as searchers must decide when to stop looking for additional targets, which results in high miss rates in multiple-target searches. In the study reported here, we quantified human strategies in multiple-target search via an ecological optimal foraging model and investigated whether searchers adapt their strategies to complex target-distribution statistics. Separate groups of individuals searched displays with the number of targets per trial sampled from different geometric distributions but with the same overall target prevalence. As predicted by optimal foraging theory, results showed that individuals searched longer when they expected more targets to be present and adjusted their expectations on-line during each search by taking into account the higher-order, across-trial target distributions. However, compared with modeled ideal observers, participants systematically responded as if the target distribution were more uniform than it was, which suggests that training could improve multiple-target search performance.

Stroboscopic visual training improves information encoding in short-term memory
Appelbaum, L. G., Cain, M. S., Schroeder, J. E., Darling, E. F., & Mitroff, S. R. (2012). Stroboscopic visual training improves information encoding in short-term memory. Attention, Perception, & Psychophysics, 74(8), 1681-1691.

The visual system has developed to transform an undifferentiated and continuous flow of information into discrete and manageable representations, and this ability rests primarily on the uninterrupted nature of the input. Here we explore the impact of altering how visual informa- tion is accumulated over time by assessing how intermittent vision influences memory retention. Previous work has shown that intermittent, or stroboscopic, visual training (i.e., practicing while only experiencing snapshots of vision) can enhance visual–motor control and visual cognition, yet many questions remain unanswered about the mechanisms that are altered. In the present study, we used a partial-report memory paradigm to assess the possible changes in visual memory following training under stroboscopic conditions. In Experiment 1, the memory task was completed before and immediately after a training phase, wherein participants engaged in physical activities (e.g., playing catch) while wearing either specialized stroboscopic eyewear or transparent control eyewear. In Experiment 2, an additional group of participants underwent the same stroboscopic pro- tocol but were delayed 24 h between training and assess- ment, so as to measure retention. In comparison to the control group, both stroboscopic groups (immediate and delayed retest) revealed enhanced retention of information in short-term memory, leading to better recall at longer stimulus-to-cue delays (640–2,560 ms). These results dem- onstrate that training under stroboscopic conditions has the capacity to enhance some aspects of visual memory, that these faculties generalize beyond the specific tasks that were trained, and that trained improvements can be maintained for at least a day.

Cognitive Pitfall!: Video game players are not immune from dual-task costs
Donohue, S., James, B., Eslick, A. N., & Mitroff, S. R. (2012). Cognitive Pitfall!: Video game players are not immune from dual-task costs. Attention, Perception, & Psychophysics, 74, 803-809.

With modern technological advances, we often find ourselves dividing our attention between multiple tasks. While this may seem a productive way to live, our atten- tional capacity is limited, and this yields costs in one or more of the many tasks that we try to do. Some people believe that they are immune to the costs of multitasking and commonly engage in potentially dangerous behavior, such as driving while talking on the phone. But are some groups of individuals indeed immune to dual-task costs? This study examines whether avid action videogame players, who have been shown to have heightened attentional capaci- ties, are particularly adept multitaskers. Participants complet- ed three visually demanding experimental paradigms (a driving videogame, a multiple-object-tracking task, and a visual search), with and without answering unrelated ques- tions via a speakerphone (i.e., with and without a dual-task component). All of the participants, videogame players and nonvideogame players alike, performed worse while engaging in the additional dual task for all three paradigms. This sug- gests that extensive videogame experience may not offer immunity from dual-task costs.

What is the identity of a sports spectator?
Appelbaum, L. G., Cain, M. S., Darling, E. F., Stanton, S. J., Nguyen, M. T., & Mitroff, S. R. (2012). What is the identity of a sports spectator? Personality and Individual Differences, 52, 422-427.

Despite the prominence of sports in contemporary society, little is known about the identity and person- ality traits of sports spectators. With a sample of 293 individuals, we examine four broad categories of factors that may explain variability in the reported amount of time spent watching sports. Using individ- ual difference regression techniques, we explore the relationship between sports spectating and physio- logical measures (e.g., testosterone and cortisol), clinical self-report scales (ADHD and autism), personality traits (e.g., NEO ‘‘Big Five’’), and pastime activities (e.g., video game playing). Our results indi- cate that individuals who report higher levels of sports spectating tend to have higher levels of extraver- sion, and in particular excitement seeking and gregariousness. These individuals also engage more in complementary pastime activities, including participating in sports and exercise activities, watching TV/movies, and playing video games. Notably, no differences were observed in the clinical self-report scales, indicating no differences in reported symptoms of ADHD or autism for spectators and non-spec- tators. Likewise, no relationship was seen between baseline concentrations of testosterone or cortisol and sports spectating in our sample. These results provide an assessment of the descriptive personality dimensions of frequent sports spectators and provide a basic taxonomy of how these traits are expressed across the population.

Inferring latent structure from mixed real and categorical relational data
Salazar, E., Cain, M., Darling, E., Mitroff, S., & Carin, L. (2012). Inferring latent structure from mixed real and categorical relational data.

We consider analysis of relational data (a ma- trix), in which the rows correspond to sub- jects (e.g., people) and the columns corre- spond to attributes. The elements of the matrix may be a mix of real and categori- cal. Each subject and attribute is character- ized by a latent binary feature vector, and an inferred matrix maps each row-column pair of binary feature vectors to an observed matrix element. The latent binary features of the rows are modeled via a multivariate Gaussian distribution with low-rank covari- ance matrix, and the Gaussian random vari- ables are mapped to latent binary features via a probit link. The same type construction is applied jointly to the columns. The model infers latent, low-dimensional binary features associated with each row and each column, as well correlation structure between all rows and between all columns. The Bayesian con- struction is successfully applied to real-world data, demonstrating an ability to infer mean- ingful low-dimensional structure from high- dimensional relational data.

Multiple-target visual searches—when more than 1 target can appear in a given search display—are commonplace in radiology, airport security screening, and the military. Whereas 1 target is often found accurately, additional targets are more likely to be missed in multiple-target searches. To better understand this decrement in 2nd-target detection, here we examined 2 potential forms of interference that can arise from finding a 1st target: interference from the perceptual salience of the 1st target (a now highly relevant distractor in a known location) and interference from a newly created memory repre- sentation for the 1st target. Here, we found that removing found targets from the display or making them salient and easily segregated color singletons improved subsequent search accuracy. However, replacing found targets with random distractor items did not improve subsequent search accuracy. Removing and highlighting found targets likely reduced both a target’s visual salience and its memory load, whereas replacing a target removed its visual salience but not its representation in memory. Collectively, the current experiments suggest that the working memory load of a found target has a larger effect on subsequent search accuracy than does its perceptual salience.

Distractor filtering in media multitaskers
Cain, M. S., & Mitroff, S. R. (2011). Distractor filtering in media multitaskers. Perception, 40(10), 1183- 1192.

A growing amount of modern media is consumed simultaneously, a phenomenon known as `media multitasking'. Individuals who regularly engage in this activity, heavy media multitaskers (HMMs), are more affected by irrelevant information that can intrude into a primary task than are light media multitaskers. However, the locus of this deficit is unknown, as previous research is consistent with both memory and attentional explanations. Here, we isolated attentional processes by employing a singleton distractor task with low working-memory demands. In this task, LMMs used top down information to improve their performance, yet HMMs did not. This difference in performance in an established attentional capture task argues for the presence of attentional differences in HMMs and is consistent with the idea that HMMs maintain a wider attentional scope than LMMs, even when instructed otherwise.

Improved visual cognition through stroboscopic training
Appelbaum, L. G., Schroeder, J. E., Cain, M. S., & Mitroff, S. R. (2011). Improved visual cognition through stroboscopic training. Frontiers in Psychology,2:276.

Humans have a remarkable capacity to learn and adapt, but surprisingly little research has demonstrated generalized learning in which new skills and strategies can be used flexibly across a range of tasks and contexts. In the present work we examined whether general- ized learning could result from visual–motor training under stroboscopic visual conditions. Individuals were assigned to either an experimental condition that trained with stroboscopic eyewear or to a control condition that underwent identical training with non-stroboscopic eyewear. The training consisted of multiple sessions of athletic activities during which par- ticipants performed simple drills such as throwing and catching. To determine if training led to generalized benefits, we used computerized measures to assess perceptual and cognitive abilities on a variety of tasks before and after training. Computer-based assess- ments included measures of visual sensitivity (central and peripheral motion coherence thresholds), transient spatial attention (a useful field of view – dual task paradigm), and sustained attention (multiple-object tracking). Results revealed that stroboscopic training led to significantly greater re-test improvement in central visual field motion sensitivity and transient attention abilities. No 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 suggest that stroboscopic training can effectively improve some, but not all aspects of visual perception and attention.

Anticipatory anxiety hinders detection of a second target in dual-target search
Cain, M. S., Dunsmoor, J. E., LaBar, K. S., & Mitroff, S. R. (2011). Anticipatory anxiety hinders detection of a second target in dual-target search. Psychological Science, 22, 866-871.

Professional visual searches (e.g., baggage screenings, military searches, radiological examinations) are often conducted in high-pressure environments and require focus on multiple visual targets.Yet laboratory studies of visual search tend to be conducted in emotionally neutral settings with only one possible target per display. In the experiment reported here, we looked to better emulate high-pressure search conditions by presenting searchers with arrays that contained between zero and two targets while inducing anticipatory anxiety via a threat-of-shock paradigm. Under conditions of anticipatory anxiety, dual-target performance was negatively affected, but single-target performance and time on task were unaffected. These results suggest that multiple-target searches may be a more sensitive instrument to measure the effect of environmental factors on visual cognition than single-target searches are. Further, the effect of anticipatory anxiety was modulated by individual differences in state anxiety levels of participants prior to the experiment.These results have implications for both the laboratory study of visual search and the management and assessment of professional searchers.

Enhanced change detection performance reveals improved strategy use in avid action video game players
Clark, K., Fleck, M. S., & Mitroff, S. R. (2011). Enhanced change detection performance reveals improved strategy use in avid action video game players. Acta Psychologica, 136, 67-72.

Recent research has shown that avid action video game players (VGPs) outperform non-video game players (NVGPs) on a variety of attentional and perceptual tasks. However, it remains unknown exactly why and how such differences arise; while some prior research has demonstrated that VGPs' improvements stem from enhanced basic perceptual processes, other work indicates that they can stem from enhanced attentional control. The current experiment used a change-detection task to explore whether top-down strategies can contribute to VGPs' improved abilities. Participants viewed alternating presentations of an image and a modified version of the image and were tasked with detecting and localizing the changed element. Consistent with prior claims of enhanced perceptual abilities, VGPs were able to detect the changes while requiring less exposure to the change than NVGPs. Further analyses revealed this improved change detection performance may result from altered strategy use; VGPs employed broader search patterns when scanning scenes for potential changes. These results complement prior demonstrations of VGPs' enhanced bottom-up perceptual benefits by providing new evidence of VGPs' potentially enhanced top-down strategic benefits.

Dynamics of population response to changes of motion direction in primary visual cortex
Wu, W., Tiesinga, P., Tucker, T., Heiner, J., Mitroff, S. R., & Fitzpatrick, D. (2011). Dynamics of Population Response to Changes of Motion Direction in Primary Visual Cortex. Journal of Neuroscience, 31(36), 12767-12777.

The visual system is thought to represent the direction of moving objects in the relative activity of large populations of cortical neurons that are broadly tuned to the direction of stimulus motion, but how changes in the direction of a moving stimulus are represented in the population response remains poorly understood. Here we take advantage of the orderly mapping of direction selectivity in ferret primary visual cortex (V1) to explore how abrupt changes in the direction of a moving stimulus are encoded in population activity using voltage- sensitive dye imaging. For stimuli moving in a constant direction, the peak of the V1 population response accurately represented the direction of stimulus motion, but following abrupt changes in motion direction, the peak transiently departed from the direction of stimulus motion in a fashion that varied with the direction offset angle and was well predicted from the response to the component directions. We conclude that cortical dynamics and population coding mechanisms combine to place constraints on the accuracy with which abrupt changes in direction of motion can be represented by cortical circuits.

Video game players show more precise multisensory temporal processing abilities
Donohue, S. E., Woldorff, M. G., & Mitroff, S. R. (2010). Video game players show more precise multisensory temporal processing abilities. Attention, Perception, & Psychophysics, 72, 1120-1129.

Recent research has demonstrated enhanced visual attention and visual perception in individuals with ex- tensive experience playing action video games. These benefits manifest in several realms, but much remains unknown about the ways in which video game experience alters perception and cognition. In the present study, we examined whether video game players’ benefits generalize beyond vision to multisensory processing by presenting auditory and visual stimuli within a short temporal window to video game players and non–video game players. Participants performed two discrimination tasks, both of which revealed benefits for video game players: In a simultaneity judgment task, video game players were better able to distinguish whether simple visual and auditory stimuli occurred at the same moment or slightly offset in time, and in a temporal-order judg- ment task, they revealed an enhanced ability to determine the temporal sequence of multisensory stimuli. These results suggest that people with extensive experience playing video games display benefits that extend beyond the visual modality to also impact multisensory processing.

See an object, hear an object file: Object correspondence transcends sensory modality
Jordan, K. E., Clark, K., & Mitroff, S. R. (2010). See an object, hear an object file: Object correspondence transcends sensory modality. Visual Cognition, 18, 492-503.

An important task of perceptual processing is to parse incoming information into distinct units and to keep track of those units over time as the same, persisting representations. Within the study of visual perception, maintaining such persisting object representations is helped by ‘‘object files’’*episodic representations that store (and update) information about objects’ properties and track objects over time and motion via spatiotemporal information. Although object files are typically discussed as visual, here we demonstrate that object file correspondence can be computed across sensory modalities. An object file can be initially formed with visual input and later accessed with corresponding auditory information, suggesting that object files may be able to operate at a multimodal level of perceptual processing.

Generalized ‘satisfaction of search’: Adverse influences on dual-target search accuracy
Fleck, M. S., Samei, E., & Mitroff, S. R. (2010). Generalized ‘satisfaction of search’: Adverse influences on dual-target search accuracy. Journal of Experimental Psychology: Applied, 16, 60-71.

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). Given the potential consequences, here we inves- tigate the generality of SOS with the goal of simultaneously informing radiology, cognitive psychology, and nonmedical searches such as airport luggage screening. Ten experiments utilizing nonmedical searches and untrained searchers suggest that SOS is affected by a diverse array of factors, including (1) the relative frequency of different target types, (2) external pressures (reward and time), and (3) expectations about the number of targets present. Collectively, these experiments indicate that SOS arises when searchers have a biased expectation about the low likelihood of specific targets or events, and when they are under pressure to perform efficiently. This first demonstration of SOS outside of radiology implicates a general heuristic applicable to many kinds of searches. In an example like airport luggage screening, the current data suggest that the detection of an easy-to-spot target (e.g., a water bottle) might reduce detection of a hard-to-spot target (e.g., a box cutter).

Generalization of conditioned fear along a dimension of increasing fear intensity
Dunsmoor, J. E., Mitroff, S. R., & LaBar, K. S. (2009). Generalization of conditioned fear along a dimension of increasing fear intensity. Learning & Memory, 16, 460-469.

The present study investigated the extent to which fear generalization in humans is determined by the amount of fear intensity in nonconditioned stimuli relative to a perceptually similar conditioned stimulus. Stimuli consisted of graded emotionally expressive faces of the same identity morphed between neutral and fearful endpoints. Two experimental groups underwent discriminative fear conditioning between a face stimulus of 55% fear intensity (conditioned stimulus, CS+), reinforced with an electric shock, and a second stimulus that was unreinforced (CS ). In Experiment 1 the CS was a relatively neutral face stimulus, while in Experiment 2 the CS was the most fear-intense stimulus. Before and following fear conditioning, skin conductance responses (SCR) were recorded to different morph values along the neutral-to-fear dimension. Both experimental groups showed gradients of generalization following fear conditioning that increased with the fear intensity of the stimulus. In Experiment 1 a peak shift in SCRs extended to the most fear-intense stimulus. In contrast, generalization to the most fear-intense stimulus was reduced in Experiment 2, suggesting that discriminative fear learning procedures can attenuate fear generalization. Together, the findings indicate that fear generalization is broadly tuned and sensitive to the amount of fear intensity in nonconditioned stimuli, but that fear generalization can come under stimulus control. These results reveal a novel form of fear generalization in humans that is not merely based on physical similarity to a conditioned exemplar, and may have implications for understanding generalization processes in anxiety disorders characterized by heightened sensitivity to nonthreatening stimuli.

Staying in bounds: Contextual constraints on object file coherence
Mitroff, S. R., Arita, J. T., & Fleck, M. S. (2009). Staying in bounds: Contextual constraints on object file coherence. Visual Cognition, 17, 195-211.

Coherent visual perception necessitates the ability to track distinct objects as the same entities over time and motion. Calculations of such object persistence appear to be fairly automatic and constrained by specific rules. We explore the nature of object persistence here within the object-file framework; object files are mid-level visual representations that track entities over time and motion as the same persisting objects and store and update information about the objects. We present three new findings. First, objects files are constrained by the principle of ‘‘boundedness’’; persisting entities should maintain a single closed contour. Second, object files are constrained by the principle of ‘‘containment’’; all the parts and properties of a persisting object should reside within, and be connected to, the object itself. Third, object files are sensitive to the context in which an object appears; the very same physical entity that can instantiate object-file formation in one experimental context cannot in another. This contextual influence demon- strates for the first time that object files are sensitive to more than just the physical properties contained within any given visual display.

Preserved visual representations despite change blindness in infants
Wang, S, & Mitroff, S. R. (2009). Preserved visual representations despite change blindness in infants. Developmental Science, 12, 681-687.

Combining theoretical hypotheses of infant cognition and adult perception, we present evidence that infants can maintain visual representations despite their failure to detect a change. Infants under 12 months typically fail to notice a change to an object’s height in a covering event. The present experiments demonstrated that 11-month-old infants can nevertheless maintain a viable representation of both the pre- and post-change heights despite their ‘change blindness’. These results suggest that infants, like adults, can simultaneously maintain multiple representations, even if they do not optimally use them.

Cohesion as a constraint on object persistence in infancy
Cheries, E., Mitroff, S. R., Wynn, K., & Scholl, B. J. (2008). Cohesion as a constraint on object persistence in infancy. Developmental Science, 11, 427-432.

A critical challenge for visual perception is to represent objects as the same persisting individuals over time and motion. Across several areas of cognitive science, researchers have identified cohesion as among the most important theoretical principles of object persistence: An object must maintain a single bounded contour over time. Drawing inspiration from recent work in adult visual cognition, the present study tested the power of cohesion as a constraint as it operates early in development. In particular, we tested whether the most minimal cohesion violation – a single object splitting into two – would destroy infants’ ability to represent a quantity of objects over occlusion. In a forced-choice crawling paradigm, 10- and 12-month-old infants witnessed crackers being sequentially placed into containers, and typically crawled toward the container with the greater cracker quantity. When one of the crackers was visibly split in half, however, infants failed to represent the relative quantities, despite controls for the overall quantities and the motions involved. This result helps to characterize the fidelity and specificity of cohesion as a fundamental principle of object persistence, suggesting that even the simplest possible cohesion violation can dramatically impair infants’ object representations and influence their overt behavior.

Space and time, not surface features, underlie object persistence
Mitroff, S. R., & Alvarez, G. A. (2007). Space and time, not surface features, underlie object persistence. Psychonomic Bulletin & Review. 14, 1199-1204.

Successful visual perception relies on the ability to keep track of distinct entities as the same persisting objects from one moment to the next. This is a computationally difficult process and its underlying nature remains un- clear. 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. From six experiments we find that spatiotemporal information (location as a function of time) easily determines object files, but surface features do not. The results suggest an unexpectedly strong constraint on the visual system’s ability to compute online object persistence.

Rare targets are rarely missed in correctable search
Fleck, M. S., & Mitroff, S. R. (2007). Rare targets are rarely missed in correctable search. Psychological Science, 18, 943-947.

Failing to find a tumor in an x-ray scan or a gun in an airport baggage screening can have dire conse- quences, making it fundamentally important to elucidate the mechanisms that hinder performance in such visual searches. Recent laboratory work has indicated that low target prevalence can lead to disturbingly high miss rates in visual search. Here, however, we demonstrate that misses in low-prevalence searches can be readily abated. When targets are rarely present, observers adapt by re- sponding more quickly, and miss rates are high. Critically, though, these misses are often due to response-execution errors, not perceptual or identification errors: Observers know a target was present, but just respond too quickly. When provided an opportunity to correct their last re- sponse, observers can catch their mistakes. Thus, low target prevalence may not be a generalizable cause of high miss rates in visual search.

Reversing how to think about ambiguous figure reversals: Spontaneous alternating by uninformed observers
Mitroff, S. R., Sobel, D. M., Gopnik, A. (2006). Reversing how to think about ambiguous figure reversals: Spontaneous alternating by uninformed observers. Perception, 35, 709-715. 53.

Ambiguous figures are a special class of images that can give rise to multiple inter- pretations. Traditionally, switching between the possible interpretations of an ambiguous figure, or reversing one's interpretation, has been attributed either to top-down or to bottom-up processes (eg attributed to having knowledge of the nature of the ambiguity, or to a form of neuronal fatigue). Here we present evidence that is incompatible with both forms of explanations. Observers aged 5-9 years can reverse ambiguous figures when uninformed about the ambiguity, negating purely top-down explanations. Further, those children who make these "spontaneous" reversals are more likely to succeed on a high-order theory-of-mind task, negating purely bottom up explanations.

The persistence of object file representations
Noles, N. S., Scholl, B. J., & Mitroff, S. R. (2005). The persistence of object file representations. Perception & Psychophysics, 67, 324-334. 54.

Coherent visual experience of dynamic scenes requires not only that the visual system segment scenes into component objects but that these object representations persist, so that an object can be identified as the same object from an earlier time. Object files (OFs) are visual representations thought to mediate such abilities: OFs lie between lower level sensory processing and higher level recognition, and they track salient objects over time and motion. OFs have traditionally been studied via object- specific preview benefits (OSPBs), in which discriminations of an object’s features are speeded when an earlier preview of those features occurred on the same object, as opposed to on a different object, beyond general displaywide priming. Despite its popularity, many fundamental aspects of the OF frame- work remain unexplored. For example, although OFs are thought to be involved primarily in online vi- sual processing, we do not know how long such representations persist; previous studies found OSPBs for up to 1,500msec but did not test for longer durations. We explored this issue using a modified ob- ject reviewing paradigm and found that robust OSPBs persist for more than five times longer than has previously been tested—for at least 8 sec, and possibly for much longer. Object files may be the “glue” that makes visual experience coherent not just in online moment-by-moment processing, but on the scale of seconds that characterizes our everyday perceptual experiences. These findings also bear on research in infant cognition, where OFs are thought to explain infants’ abilities to track and enumer- ate small sets of objects over longer durations.

The relationship between object files and conscious perception
Mitroff, S. R., Scholl, B. J., & Wynn, K. (2005). The relationship between object files and conscious perception. Cognition, 96, 67-92. 55.

Object files (OFs) are hypothesized mid-level representations which mediate our conscious perception of persisting objects—e.g. telling us ‘which went where’. Despite the appeal of the OF framework, not previous research has directly explored whether OFs do indeed correspond to conscious percepts. Here we present at least one case wherein conscious percepts of ‘which went where’ in dynamic ambiguous displays diverge from the analogous correspondence computed by the OF system. Observers viewed a ‘bouncing/streaming’ display in which two identical objects moved such that they could have either bounced off or streamed past each other. We measured two dependent variables: (1) an explicit report of perceived bouncing or streaming; and (2) an implicit ‘object- specific preview benefit’ (OSPB), 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 (compared to when it reappears on a different object), beyond display-wide priming. When the displays were manipulated such that observers had a strong bias to perceive streaming (on over 95% of the trials), there was nevertheless a strong OSPB in the opposite direction—such that the object files appeared to have ‘bounced’ even though the percept ‘streamed’. Given that OSPBs have been taken as a hallmark of the operation of object files, the five experiments reported here suggest that in at least some specialized (and perhaps ecologically invalid) cases, conscious percepts of ‘which went where’ in dynamic ambiguous displays can diverge from the mapping computed by the object-file system.

Forming and updating object representations without awareness: Evidence from motion-induced blindness
Mitroff, S. R. & Scholl, B. J. (2005). Forming and updating object representations without awareness: Evidence from motion-induced blindness. Vision Research, 45, 961-967. 56.

The input to visual processing consists of an undifferentiated array of features which must be parsed into discrete units. Here we explore the degree to which conscious awareness is important for forming such object representations, and for updating them in the face of changing visual scenes. We do so by exploiting the phenomenon of motion-induced blindness (MIB), where in salient (and even attended) objects fluctuate into and out of conscious awareness when superimposed onto certain global motion patterns. By introducing changes to unseen visual stimuli during MIB, we demonstrate that object representations can be formed and updated even without conscious access to those objects. Such changes can then influence not only how stimuli reenter awareness, but also what reenters awareness. We demonstrate that this processing encompasses simple object representations and also several independent Gestalt grouping cues. We conclude that flexible visual parsing over time and visual change can occur even without conscious perception. Methodologically, we conclude that MIB may be an especially useful tool for studying the role of awareness in visual processing and vice versa.

Seeing the disappearance of unseen objects
Mitroff, S. R. & Scholl, B. J. (2004). Seeing the disappearance of unseen objects. Perception, 33, 1267- 1273. 57.

Because of the massive amount of incoming visual information, perception is funda- mentally selective. We are aware of only a small subset of our visual input at any given moment, and a great deal of activity can occur right in front of our eyes without reaching awareness. While previous work has shown that even salient visual objects can go unseen, here we demon- strate the opposite pattern, wherein observers perceive stimuli which are not physically present. In particular, we show in two motion-induced blindness experiments that unseen objects can momentarily reenter awareness when they physically disappear: in some situations, you can see the disappearance of something you can't see. Moreover, when a stimulus changes outside of awareness in this situation and then physically disappears, observers momentarily see the altered versionöthus perceiving properties of an object that they had never seen before, after that object is already gone. This phenomenon of `perceptual reentry' yields new insights into the relationship between visual memory and conscious awareness.

Divide and conquer: How object files adapt when a persisting object splits into two
Mitroff, S. R., Scholl, B. J., & Wynn, K. (2004). Divide and conquer: How object files adapt when a persisting object splits into two. Psychological Science, 15, 420-425. 58.

Coherent visual experience requires not only seg- menting incoming visual input into a structured scene of objects, but also binding discrete views of objects into dynamic rep- resentations that persist across time and motion. However, surprisingly little work has explored the principles that guide the construction and maintenance of such persisting object rep- resentations. What causes a part of the visual field to be treated as the same object over time? In the cognitive development lit- erature, a key principle of object persistence is cohesion: An object must always maintain a single bounded contour. Here we demonstrate for the first time that mechanisms of adult midlevel vision are affected by cohesion violations. Using the object-file framework, we tested whether object-specific preview benefits—a hallmark of persisting object representa- tions—are obtained for dynamic objects that split into two during their motion. We found that these preview benefits do not fully persist through such cohesion violations without incurring significant performance costs. These results illustrate how cohesion is employed as a constraint that guides the main- tenance of object representations in adult midlevel vision.

Nothing compares 2 views: Change blindness can occur despite preserved access to the changed information
Mitroff, S. R., Simons, D. J., & Levin, D. T. (2004). Nothing compares 2 views: Change blindness can occur despite preserved access to the changed information. Perception & Psychophysics, 66, 1268-1281. 59.

Change blindness, the failure to detect visual changes that occur during a disruption, has increas- ingly been used to infer the nature of internal representations. If every change were detected, detailed representations of the world would have to be stored and accessible. However, because many changes are not detected, visual representations might not be complete, and access to them might be limited. Using change detection to infer the completeness of visual representations requires an understanding of the reasons for change blindness. This article provides empirical support for one such reason: change blindness resulting from the failure to compare retained representations of both the pre- and postchange information. Even when unaware of changes, observers still retained information about both the pre- and postchange objects on the same trial.

Changes are not localized until they are explicitly detected
Mitroff, S. R. & Simons, D. J. (2002). Changes are not localized until they are explicitly detected. Visual Cognition, 9, 937-968. 60.

Change detection is in many ways analogous to visual search. Yet, unlike search, successful detection depends not on the salience of features within a scene, but on the difference between the original and modified scene. If, as in search, pre- attentive mechanisms guide attention to the change location, the change itself must produce a preattentively detectable signal. Despite recent evidence for implicit representation of change in the absence of conscious detection, few studies have yet explored whether attention is guided to a change location prior to explicit detection. In four ‘‘change blindness’’ experiments using several variants of the ‘‘flicker’’ task, we tested the hypothesis that implicit or preattentive mechanisms guide change localization prior to explicit detection. None of the experiments revealed improved localization of changes prior to explicit reports of detection, suggesting that implicit detection of change does not contribute to the eventual explicit localization of a change. Instead, change localization is essentially arbi- trary, driven by the salience of features within scenes.

The siren song of implicit change detection
Mitroff, S. R., Simons, D. J., & Franconeri, S. L. (2002). The siren song of implicit change detection. Journal of Experimental Psychology: Human Perception and Performance, 28, 798-815.

Although change blindness could suggest that observers represent far less of their visual world than their conscious experience leads them to believe, they could fail to detect changes even if they fully represent all details. Reports of implicit change detection in the absence of awareness are consistent with the notion that observers’ representations are more complete than previously thought. However, to provide con- vincing evidence, studies must separate implicit detection from explicit processes. This article reexam- ines the 3 primary claims of implicit change detection and, after replicating original findings, provides theoretical and empirical support for alternative, explicit explanations. Even if observers do represent more of the scene than previously thought, change detection might occur only through explicit comparisons.

Paper Abstracts