Stephen H. Adamo

Self-Induced Attentional Blink A Cause of Errors in Multiple-Target Search

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.

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.

Examining perceptual and conceptual set biases in multiple-target visual search

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 targets that are dissimilar to the first target. This particular hypothesis 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 substantially reduced when the two targets were identical, suggesting that the first-found target did indeed create biases during subsequent 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 implications for visual-search theories and applications for professional visual searchers.

Targets Need Their Own Personal Space: Effects of Clutter on Multiple-Target Search Accuracy

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.

What eye-tracking can tell us about multiple-target visual search

• Half of Satisfaction of Search errors were due to faulty scanning: searchers never fixated the second target, likely due to both scanning problems (i.e., an ineffective search pattern) and strategic problems (i.e., not searching long enough) • Recognition and Decision Errors account for the other half, with Recognition Errors more prevalent • This pattern is reversed from that found in radiology, where Decision Errors were most common, suggesting that the relative contributions of error types are influenced by the nature of the search and searchers • Refixating previously found targets contributed to Satisfaction of Search errors, imparing search efficiency • Strategic Errors contributed overtly to some trials, but likely contrubuted subtly to many Scanning Errors Breakdown of Second-Target Miss Errors

Satisfaction at last: Evidence for the “satisfaction” hypothesis for multiple-target search errors

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

Mo' Money, Mo' Problems: Monetary Motivation Can Exacerbate the Attentional Blink

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.

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.

Satisfaction at last: evidence for the 'satisfaction' account for multiple-target search errors.

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.

Self-induced attentional blink: A cause of errors in multiple-target visual search

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