Memory and Recognition of a Non-Target During a Threat Detection Visual Search Task

Abstract

Context plays an important role in visual search tasks. The ability of people to form implicit associations about the objects in the world around them not only assists them in focusing their attention but also in simplifying their world. The goal of this study was to investigate whether, and how, people utilize “distractors” as contextual cues during a visual target search. Twenty undergraduate participants performed a luggage-screening task, where they were asked to locate a specific target (a knife). First, participants were trained using 25 luggage images, each of which contained a target (i.e., knife) and a specific distractor (i.e., iPod). During the post-training session, participants screened 100 bags with target base rate set at 50%. The bags contained either the distractor and the target (25 bags), the target only (25 bags), the distractor only (25 bags), or neither the distractor nor the target (25 bags). Participants’ dwell times and fixation counts for specific areas of interest (AOI) were assessed across trial blocks. It was found that recognition of the distractor object increased across trials but the dwell time and number of fixations decreased as the experiment progressed. These results demonstrate that participants were able to recognize the distractor and form an implicit association between its presence and the presence of the target. Results also indicated that the presence of the distractor ultimately biased participant response, creating more “liberal” responses over time.