Abstract
According to the Load theory of attention, the perceptual processing of irrelevant information is determined automatically in response to the perceptual demands of processing task-relevant information (e.g. Lavie, 1995; Lavie, Hirst, De Fockert, & Viding, 2004). Because of the assumption of automaticity, increases in perceptual load should reduce task-irrelevant processing irrespective of the distractor-target relationship. While research has supported the modulation of distraction as a function of perceptual load (Lavie, Hirst, DeFockert, & Viding, 2004; Wei, & Zhou, 2006), tests of task-irrelevant processing have typically confounded the relative influence of target-distractor similarity on multiple dimensions (i.e., feature and response compatibility). The purpose of the present experiment was to isolate the relative contribution of these factors. Participants (n = 17) were instructed to identify the category of a centrally presented stimulus (‘d’ or ‘q’) while ignoring irrelevant flankers presented in the periphery. There were two key manipulations: 1) target-distractor relationship was manipulated such that distractors can share neither feature nor response (‘S’ or ‘G’), share only features (‘b’ or ‘p’), share only responses (‘Q’ or ‘D’), or share both feature and response (‘d’ or ‘q’) with the target and 2) load was manipulated by incrementally shifting the ‘o’ target feature vertically making the stimulus category more or less ambiguous. The results indicated that performance was modulated by the target-distractor relationship even under conditions of high perceptual load. Thus, these results support the conclusion that perceptual load is not the only determinant of the behavioral interference caused by task-irrelevant information, but rather that the amount of distraction is also influenced by the degree to which task-irrelevant information matches one’s current attentional set.