Pop-out from abrupt visual onsets

Abstract

We report a novel psychophysical paradigm that distinguishes the information present in abrupt stimulus onset from that in the following display. The task is to pick the one odd item from a set added to a pre-existing background of similar items. When all new items are added simultaneously, observers are impaired even at distinguishing one red item amongst several green ones. An asynchrony of about 40ms between target and distracter items restores performance, with evidence that it is cortical, rather than stimulus timing difference that is significant. The results are consistent with a role for neural synchrony in dynamic grouping.