Frieder, K, & Carrasco, M (2001, May). Negative priming for unfamiliar shapes occurs under covert attention. Vision ScienceS Society, Sarasota, FL. 211-B11.

Abstract
Introduction and Goal: In this study, for the first time, we explored whether the selective processing of an unfamiliar shape at the attended location is influenced by information outside the locus of attention even when the short duration of the display precluded eye movements. We examined the effects of a distracter in the unattended hemifield on the processing of the target in the attended hemifield.

Method: To test the effect of unattended items, we employed a modified Negative Priming (NP) task that required a symmetry judgment of a target. Observers viewed a series of displays with a pair of overlapping shapes (a lateralized green target was overlapping a red distracter). Observers had to determine whether the target was symmetrical or not. Experimental trials were paired so that a "Prime" trial was followed by a "Test" trial. Following a negative priming paradigm, unbeknownst to the observers, in the Priming Condition, the red overlapping-distracter in the Prime trial re-appeared as the green target in the following Test trial. In the Control condition, al the shapes were novel. In Condition 1, nothing appeared in the opposite hemifield; in Condition 2 an additional black shape appeared contralaterally. RTs and errors were analyzed.

Results and Conclusion: For the first time, we report a highly significant NP effect for unfamiliar shapes under cover attention. More specifically, RTs and errors were higher when the target was seen previously as the overlapping-distracter than when the target was novel. Surprisingly, even when the display was presented for less than 200ms, participants processed the task-irrelevant overlapping-distracter, in all three conditions. Thus, NP for unfamiliar shapes occurs under covert attention.