Contextual Cueing Effects in Visual Threat Detection

Contextual cueing is the implicit association of objects ( or "cues") in a visual scene due to repeated exposure, either spatially or semantically. Associations between objects in a visual scene have been shown to aid people in detecting a specific target more quickly and easily during a visual search. The goal of this study was to investigate whether an individual could utilize a "distractor" as a contextual cue during a visual target search. Twenty undergraduate participants performed a luggage screening task during which they were connected to an eye tracker and screened 375 x-ray luggage images across three trial blocks ( each block consisting of 125 images). Participants were first trained using 25 luggage images, each of which contained a target (i.e., knife) anda specific distractor (i.e., iPod). During the post-training session, participants screened 100 bags with a target base rate of 50%. Results revealed that when the distractor was presented with a target, fixation durations increased while fixation counts, dwell times, and saccade counts decreased, and target detection was faster. We contend that participants formed an implicit association between the distractor and the target reinforced by the liberal response criterion they demonstrated. Individuals exhibited a bias towards target presence when the distractor appeared raising concerns over the ease with which the potential exists to bias a person during a visual target search. This becomes a concern for those whose jobs rely on the ability to accurately detect a target in a visual scene such as airport security luggage screeners.