The Influence of Clutter on Target Prevalence and Decision Making

Abstract

The current study aimed to identify how set size and clutter influence the target prevalence effect and participants’ decision-making during visual search. Low target prevalence leads to shorter search times and an increased miss rate, with the opposite being true for high target prevalence. Both increased set size and clutter should require more attention shifts between items (attention for recognition) leading to longer search times. However, if spacing between items is held constant as set size increases, only increased clutter should affect attention needed to inhibit the information crowding items (attention against competition) leading to longer target decisions in response to increased clutter. Participants in Experiment 1 viewed a display of either a small (10 items) or large (40 items) set size composed of rotated and offset Ls. On each trial, participants had to determine whether a rotated target T was present or absent. In Experiment 2, participants searched for a single bump elevation marker within either a low or high cluttered map. In both experiments, a target appeared on 10% of trials for low target prevalence and 90% for high target prevalence. In Experiment 1, attention for recognition altered the target prevalence effect by making participants search longer in response to more attention shifts (large set size). In Experiment 2, clutter altered the target prevalence effect, making participants search longer in response to high clutter (attention for recognition) and getting rid of the target prevalence effect for the false alarm rate and in response to low clutter for the miss rate (attention against competition). Our results suggest that attention for recognition and attention against competition impact the target prevalence effect by altering participants’ decision making, and this pattern of results can be explained using the Multiple-Decision Model (MDM) of visual search.