Evidence for early selection: precuing target location reduces interference from same-category distractors.

In this study, we evaluated whether uncertainty about target location and category overlap between the target and the flankers played a role in recent findings (Miller, 1987) of semantic interference of irrelevant stimuli. In each of four testing conditions, subjects were required to identify a target letter surrounded by irrelevant flankers whose identity predicted the correct response. We varied (1) whether or not the target location was precued, and (2) the flanker's category (digits vs. letters). We found a substantial effect of letter flankers when subjects were uncertain of the precise target location. However, this effect was greatly attenuated when attention was predirected to the target location. Similarly, a reduced flanker effect was observed when the flankers (digits) belonged to a different semantic category than the target. However, when the target location was precued, no effect of the semantic congruity of target and flankers was found. Coupled with previous research, these findings converge in establishing that both failures to maintain attention on the target location and the semantic congruity of target and flankers modulate the size of the effects from irrelevant stimuli. These results are discussed in the context of early and late selection views of selective attention.