Browsing by Subject "Visual search"

A pervasive aspect of daily life is searching for a specific target amongst an array of distracting items. Studying such visual searches offers a useful and powerful tool for revealing the underlying aspects of visual attention. Understanding how factors influence accurate target detection serves to both enhance real-world search tasks and inform basic cognitive psychology. The goal of the research presented herein is to examine the effects of expectation, experience, and environment on search behavior. The experiments are conducted in controlled laboratory environments, but are designed to simulate real-world searches, with the express goal of informing the implementation of search tasks in everyday life. First, expectation is explored by manipulating target prevalence and measuring the resultant change in behavior as participants' biases shift. Second, experience is tested by comparing individuals with and without extensive video game exposure, specifically on their susceptibility to the pressures of rare target search. Lastly, environment is examined by utilizing multiple simultaneous targets. This manipulation has been shown to induce errors in radiology, and here the generality of this effect is explored to establish the various pressures to which it is sensitive. Collectively, these data serve to inform how different influences modulate visual search performance, and the results can directly inform the training, recruitment, and execution of real-world search tasks such as those in radiology, cytology, and airport security.

For over 50 years, the Satisfaction of Search effect, and more recently known as the Subsequent Search Miss (SSM) effect, has plagued the field of radiology. Defined as a decrease in additional target accuracy after detecting a prior target in a visual search, SSM errors are known to underlie both real-world search errors (e.g., a radiologist is more likely to miss a tumor if a different tumor was previously detected) and more simplified, lab-based search errors (e.g., an observer is more likely to miss a target ‘T’ if a different target ‘T’ was previously detected). Unfortunately, little was known about this phenomenon’s cognitive underpinnings and SSM errors have proven difficult to eliminate. However, more recently, experimental research has provided evidence for three different theories of SSM errors: the Satisfaction account, the Perceptual Set account, and the Resource Depletion account. A series of studies examined performance in a multiple-target visual search and aimed to provide support for the Resource Depletion account—a first target consumes cognitive resources leaving less available to process additional targets.

To assess a potential mechanism underlying SSM errors, eye movements were recorded in a multiple-target visual search and were used to explore whether a first target may result in an immediate decrease in second-target accuracy, which is known as an attentional blink. To determine whether other known attentional distractions amplified the effects of finding a first target has on second-target detection, distractors within the immediate vicinity of the targets (i.e., clutter) were measured and compared to accuracy for a second target. To better understand which characteristics of attention were impacted by detecting a first target, individual differences within four characteristics of attention were compared to second-target misses in a multiple-target visual search.

The results demonstrated that an attentional blink underlies SSM errors with a decrease in second-target accuracy from 135ms-405ms after detection or re-fixating a first target. The effects of clutter were exacerbated after finding a first target causing a greater decrease in second-target accuracy as clutter increased around a second-target. The attentional characteristics of modulation and vigilance were correlated with second- target misses and suggest that worse attentional modulation and vigilance are predictive of more second-target misses. Taken together, these result are used as the foundation to support a new theory of SSM errors, the Flux Capacitor theory. The Flux Capacitor theory predicts that once a target is found, it is maintained as an attentional template in working memory, which consumes attentional resources that could otherwise be used to detect additional targets. This theory not only proposes why attentional resources are consumed by a first target, but encompasses the research in support of all three SSM theories in an effort to establish a grand, unified theory of SSM errors.

Visual search, the process of detecting relevant items within an environment, is a vital skill required for navigating one's visual environment as well as for careers, such as radiology and airport security, that rely upon accurate searching. Research over the course of several decades has established that visual search requires the integration of low- and high-level cognitive processes, including sensory analysis, attentional allocation, target discrimination, and decision-making. Search abilities are malleable and vary in accordance with long-term experiences, direct practice, and contextual factors in the immediate environment; however, the mechanisms responsible for changes in search performance remain largely unclear. A series of studies examine variation in visual search abilities and performance and aim to identify the underlying mechanisms.

To assess differences associated with long-term experiences, visual search performance is compared between laypersons (typically undergraduates) and specific populations, including radiologists and avid action video game players. Behavioral markers of search processes are used to elucidate causes of enhanced search performance. To assess differences associated with direct practice, laypersons perform a visual search task over five consecutive days, and electrophysiological activity is recorded from the scalp on the first and last days of the protocol. Electrophysiological markers associated with specific stages of processing are analyzed to determine neurocognitive changes contributing to improved performance. To assess differences associated with contextual factors, laypersons are randomly assigned to experimental conditions in which they complete a visual search task within a particular framework or in the presence or absence of motivation, feedback, and/or time pressure.

Results demonstrate that search abilities can improve through experience and direct training, but the mechanisms underlying effects in each case are different. Long-term experiences are associated with strategic attentional allocation, but direct training can improve low-level sensory analysis in addition to higher-level processes. Results also demonstrate nuanced effects of experience and context. On searches that contain multiple targets, task framework impacts accuracy for detecting additional targets after one target has been identified. The combination of motivation and feedback enhances accuracy for both single- and multiple-target searches. Implications for cognitive theory and applications to occupational protocols are discussed.