Academic journal article Perception and Psychophysics

When Do Irrelevant Visual Stimuli Impair Processing of Identical Targets?

Academic journal article Perception and Psychophysics

When Do Irrelevant Visual Stimuli Impair Processing of Identical Targets?

Article excerpt

Three experiments investigated whether the repeated-letter inferiority effect (RLIE) and repetition blindness (RB) are identical phenomena or not and how the RLIE can be reconciled with the flanker compatibility effect (FCE). Participants reported a masked target and ignored an unmasked distractor. We manipulated the type of distractor (identical, alternative target, or neutral), the order of presenting distractor and target, and the predictability of target location. When distractors preceded the targets, distractors identical to the target always caused deficits in target processing (i.e., RB). With simultaneous presentation, identical distractors caused deficits (i.e., an RLIE) for unpredictable target locations only. Yet the RLIE was significantly smaller than RB. This result suggests that simultaneously presented stimuli are identified serially, in random order, if target position is unpredictable. As a result, RB arises only in the 50% of all trials with identical distractors in which the distractor is identified before the target. With simultaneous presentation and predictable target location, however, parallel processing of targets and distractors was possible that gave rise to an FCE in recognition accuracy. Analyses of false alarm rates revealed no evidence of significant response biases.

An informative tool for investigating visual perception in humans has been to study the effects of identical distractors (i.e., not-to-be-reported stimuli that are identical to the target) on processing of a target stimulus (i.e., a tobe-reported stimulus). Such investigations have discovered many interesting phenomena, and to explain them, researchers have suggested many functional mechanisms of visual processing. Among these phenomena are the repeated-letter inferiority effect (RLIE; Egeth & Santee, 1981), repetition blindness (RB; Kanwisher, 1987), redundancy gain (RG; Miller, 1982), and the flanker compatibility effect (FCE; B. A. Eriksen & C. W. Eriksen, 1974). On the other hand, similar experimental situations have produced conflicting empirical observations (e.g., RLIE vs. RG). Moreover, different explanations have been proposed to explain similar phenomena that occur in different situations (e.g., RB vs. RLIE). The goal of the present study is to resolve at least some of these empirical and theoretical discrepancies. In particular, the study addresses discrepancies between the RLIE and the phenomena of RB, RG, and FCE. In the following sections, the phenomena and the pairwise discrepancies among them are described, and a theoretical solution for these discrepancies is presented. Finally, three experiments are reported that tested the new account.

Repeated-Letter Inferiority Effect

Bjork and Murray ( 1977) investigated the effects of simultaneously presented identical and nonidentical distractors in a visual display on the accuracy of identifying a target. Participants observed two simultaneously presented letters that were preceded and followed by a mask. The letters appeared in different columns of a 4 × 4 matrix, and a postcue indicated the column that had to be responded to. Participants then decided which of two letters specified in advance had been presented in the cued column. The result was that repeated letters in the display decreased identification accuracy for the target. More precisely, identification performance was impaired with an identical distractor when compared with performance with a neutral distractor (i.e., a letter never presented as a target). A further result was that an incompatible distractor (i.e., the alternative target) allowed for performance similar to that with a neutral distractor. Subsequent studies have replicated and extended this finding (Egeth & Santee, 1981; Keren & Boer, 1985; Santee & Egeth, 1980, 1982).

Bjork and Murray ( 1977) explained this RLIE by assuming interactions between early visual processing channels (cf. Estes, 1972, 1974). …

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