The effect of prevalence on distractor speeded search termination

Visual search can be disrupted by irrelevant salient stimuli. Recently, Moher ( Psychological Science , 31 (1), 31–42, 2020 ) found salient distractors to speed search when a target was absent and increase error rates when the target was present. That is, distractors lowered search-quitting thresholds. Nonetheless, the salient distractors Moher used were present on 50% of all trials. Since distractor prevalence has been found to influence search processes more broadly, here, we aimed to test the effect of distractor prevalence on this distractor-quitting threshold effect (QTE). To do so, we conducted two experiments. Experiment 1 compared the performance of individuals in a search task where the target was present on 50% of trials across two distractor-prevalence conditions (25% vs. 75% prevalence). Experiment 2 followed the same procedure, except with a wider probability margin (10% vs. 90% prevalence). In Experiment 1, distractor prevalence did not modulate the QTE. Critically, in Experiment 2, the QTE was modulated. For high-prevalence distractors (90%), a QTE was observed. However, as low-prevalence distractors (10%) did not speed search, no QTE was observed. One potential reason no QTE was observed was because low-prevalence distractors have significantly greater attentional capture, which washed out speeded termination effects.