Abstract

The perceptual load theory (Lavie & Tsal, 1994) and the dilution account (Tsal & Benoni, 2010) have been proposed to explain the phenomenon that the degree of irrelevant information processing decreases as the relevant stimulus-set size increases. The present study investigated the nature of the set-size effect on processing of task-irrelevant information. Under high perceptual load with a single distractor, no congruency effect was replicated in the present study. However, importantly, the congruency effect increased as the number (ratio) of distractor increased (Experiments 1 & 2). In dilution condition (Experiment 3), a larger congruency effect was found when a conflict distractor was located at the task-relevant array than at a task-irrelevant peripheral position, which is consistent with previous findings. However, an additional presentation of a distracting letter did not produce a larger congruency effect. These results indicate that the perceptual load effect by increasing the number of task-relevant items is a result of a reduced probability of attentional capture by a conflicting distractor. Furthermore, this selective processing occurs at a focused attention stage which implies that early-visual crosstalk is not an alternative explanation.