Intertrial repetition affects perception: the role of focused attention.

Implicit short-term memory plays an important role in visual search. For instance, singleton search is faster when the target and distractor features repeat on two consecutive trials than when they switch, an effect called Priming of Popout (PoP). However, whether or not PoP facilitates early perceptual/attentional processes remains controversial. To resolve discrepancies between existing findings, we tested the hypothesis that early effects of PoP occur only if attention is focused/engaged on the target. We measured search accuracy using brief displays for a fine discrimination task, which required focused attention, and for a left/right hemifield localization task, which did not. We found that PoP effects on accuracy occur only in the discrimination task. The theoretical implications are discussed.