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E. Leslie Cameron, Brooke D. Bartow; Peripheral precuing does more than reduce location uncertainty. Journal of Vision 2004;4(8):451. doi: 10.1167/4.8.451.
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© ARVO (1962-2015); The Authors (2016-present)
Peripheral precues, which indicate both when and where a target is about to appear, are commonly used to direct covert visual spatial attention. Performance is known to improve in these conditions compared to neutral precue conditions, which indicate when but not where a target is about to appear. A variety of mechanisms have been suggested to underlie this precuing (attentional) effect. Here we examine the extent to which signal enhancement and spatial uncertainty contribute to the precue effect. Three observers performed a 2-alternative orientation identification task in the presence of either a neutral or a peripheral precue. Targets were 2 cpd Gabor patches presented briefly (40 ms), alone at 4.5 degrees eccentricity. We manipulated both precue condition (neutral/peripheral) and location uncertainty (number of possible locations at which a target could appear: 1,2,4, or 8). Performance was approximately 80% correct in the neutral precue condition when the target was presented at the same location in the visual field on every trial (no uncertainty). An ANOVA revealed a main effect of uncertainty — performance decreased as location uncertainty increased, with the largest decrease observed at low levels of uncertainty, in both precue conditions. There was also a main effect of precue — performance was overall higher in the peripheral than the neutral precue condition, even though the target was presented alone, with no distracters. There was no significant interaction. We measured reaction time and found no evidence of a speed-accuracy tradeoff. In the condition in which the target appeared at a single location (no location uncertainty), all sources of external noise were eliminated and the precue effect is consistent with signal enhancement. Moreover, given that there was no significant interaction between precue and uncertainty, we suggest that signal enhancement was the main mechanism by which the peripheral precue improved performance.
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