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Zachary J.J. Roper, Joshua D. Cosman, Jonathan T. Mordkoff, Shaun P. Vecera; Perceptual load corresponds to known factors influencing visual search. Journal of Vision 2010;10(7):1277. doi: https://doi.org/10.1167/10.7.1277.
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© ARVO (1962-2015); The Authors (2016-present)
One recent account of the early versus late selection debate in attention proposes that perceptual load determines the locus of selection. Attention selects stimuli at a late processing level under low-load conditions but selects stimuli at an early level under high-load conditions. Despite the successes of so-called ‘load theory,’ the notion of perceptual load remains poorly defined. We investigated the factors that influence perceptual load by using manipulations that have been studied extensively in visual search, namely target-distractor similarity and display heterogeneity. First, using visual search, we examined the search slopes as participants discriminated two target letters. Consistent with previous work, search was most efficient when targets and distractors were dissimilar and the displays contained homogeneous distractors; search became less efficient when target-distractor similarity increased and when the displays contained heterogeneous distractors. Importantly, we next used these same stimuli in a typical perceptual load task that measured attentional ‘spill over’ to a task-irrelevant flanker. We found a correspondence between search efficiency and perceptual load; stimuli that generated efficient searches produced flanker interference effects, suggesting that such displays involved low perceptual load. Flanker interference effects were reduced in displays that produced less efficient searches, and both high target-distractor similarity and heterogeneous displays were required to abolish flanker effects. These results suggest that ‘perceptual load’ might be defined in part by well-characterized factors that influence visual search.
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