Kait Clark

A Bayesian Optimal Foraging Model of Human Visual Search

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.

Assessing visual search performance differences between Transportation Security Administration Officers and nonprofessional visual searchers

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 experienced professional searchers.

What Can 1 Billion Trials Tell Us About Visual Search

Mobile technology (e.g., smartphones and tablets) has provided psychologists with a wonderful opportunity: 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 psychological research and to provide an example roadmap of how to successfully collect usable data.

Context matters: The structure of task goals affects accuracy in multiple-target visual search

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 contained 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.

Face symmetry assessment abilities: Clinical implications for diagnosing asymmetry

INTRODUCTION An accurate assessment of face symmetry is necessary for the development of a dentofacial diagnosis in orthodontics, and an understanding of individual differences in perception of face symmetry between patients and providers is needed to facilitate successful treatment. METHODS Orthodontists, general dentists, and control participants completed a series of tasks to assess symmetry. Judgments were made on pairs of upright faces (similar to the longitudinal assessment of photographic patient records), inverted faces, and dot patterns. Participants completed questionnaires regarding clinical practice, education level, and self-confidence ratings for symmetry assessment abilities. RESULTS Orthodontists showed expertise compared with controls (P <0.001), whereas dentists showed no advantage over controls. Orthodontists performed better than dentists, however, in only the most difficult face symmetry judgments (P = 0.006). For both orthodontists and dentists, accuracy increased significantly when assessing symmetry in upright vs inverted faces (t = 3.7, P = 0.001; t = 2.7, P = 0.02, respectively). CONCLUSIONS Orthodontists showed expertise in assessing face symmetry compared with both laypersons and general dentists, and they were more accurate when judging upright than inverted faces. When using accurate longitudinal photographic records to assess changing face symmetry, orthodontists are likely to be incorrect in less than 15% of cases, suggesting that assistance from some additional technology is infrequently needed for diagnosis.

Enhanced facial symmetry assessment in orthodontists

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.

Interactions between Reward, Feedback, and Timing Structures on Dual-Target Search Performance

Individuals who conduct visual searches that can contain more than one target face many challenges. Such multiple-target visual searches can be especially error prone, as identification of one target often makes identification of a second target less likely. Given that many real-world searches can be multiple-target searches (e.g., radiological examinations, baggage screening, military searches), it is important to understand what can affect performance. Multiple-target search is particularly sensitive to top-down influences such as anticipatory anxiety (Cain, Dunsmoor, LaBar, & Mitroff, VSS 2011), and here we explore the impact of reward motivation. Participants completed a paradigm that reliably produces dual-target errors (Fleck, Samei, & Mitroff, 2010). When we simply motivated participants with a performance-based, ten-percent chance of winning an additional d50 in compensation (Experiment 1), the performance decline on dual-target trials was eliminated, while accuracy on single-target trials remained the same. Further, without monetary motivation, adding trial-by-trial feedback (Experiment 2) did not significantly improve dual-target accuracy; however, the presence of both monetary motivation and feedback (Experiment 3) resulted in substantial performance benefits for both single- and dual-target conditions compared to Experiments 1 and 2. Finally, in the presence of top-down monetary motivation, trial-based time limits (Experiment 4) did not affect performance (i.e., participants performed equivalently with or without a time limit). This is in contrast to prior data without monetary incentives (Fleck et al., 2010), in which time limits negatively affected performance. Collectively, these experiments demonstrate that (1) motivation alone is sufficient to enhance dual-target search performance, (2) such benefits are enhanced when paired with trial-by-trial feedback, and (3) time limits hurt performance in the absence of motivation but have no effect with motivation. These findings provide key information about the role of top-down motivation on performance and how this can successfully improve performance on critical dual-target searches.

The Cambridge Handbook of Applied Perception Research: Perception and Human Information Processing in Visual Search

Visual search is the process of finding specific target items within an environment using particular visual features or prior knowledge. Searches can be as easy as finding your friend with purple hair in a lecture hall or as complicated as finding a purposefully concealed weapon among thousands of harmless bags at an airport checkpoint. Visual searches take place in everyday, innocuous contexts such as finding your car in a parking lot, and in critical contexts, such as finding enemy combatants in an urban battlefield. We conduct searches all the time, and most searches are relatively commonplace. However, in some cases, visual searches can be critically important. For example, airport security screeners must identify harmful items in baggage, and radiologists must identify abnormalities in medical radiographs. Despite the ubiquitous nature of search and the fact that it is sometimes life-or-death critical, human visual search is far from ideal - errors are often made, and searches are typically conducted for either too little or too much time. Thus, some fundamental research questions are the following: How can we maximize search efficiency? What is the best way to increase both search speed and accuracy? Much academic research has focused on increasing search performance, but does such research adequately translate to situations outside the laboratory environment? These open questions are the foundation of research in applied visual search - the application of what has been learned about search accuracy and efficiency from lab-based experimentation to search conditions in the workplace for career searchers, with the goal of increasing performance.

Visual search performance is predicted by both prestimulus and poststimulus electrical brain activity

An individual’s performance on cognitive and perceptual tasks varies considerably across time and circumstances. We investigated neural mechanisms underlying such performance variability using regression-based analyses to examine trial-by-trial relationships between response times (RTs) and different facets of electrical brain activity. Thirteen participants trained five days on a color-popout visual-search task, with EEG recorded on days one and five. The task was to find a color-popout target ellipse in a briefly presented array of ellipses and discriminate its orientation. Later within a session, better preparatory attention (reflected by less prestimulus Alpha-band oscillatory activity) and better poststimulus early visual responses (reflected by larger sensory N1 waves) correlated with faster RTs. However, N1 amplitudes decreased by half throughout each session, suggesting adoption of a more efficient search strategy within a session. Additionally, fast RTs were preceded by earlier and larger lateralized N2pc waves, reflecting faster and stronger attentional orienting to the targets. Finally, SPCN waves associated with target-orientation discrimination were smaller for fast RTs in the first but not the fifth session, suggesting optimization with practice. Collectively, these results delineate variations in visual search processes that change over an experimental session, while also pointing to cortical mechanisms underlying performance in visual search.

Visual search at the airport: Testing TSA officers

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