Stimulus discrimination following covert attentional orienting to an exogenous cue.

Five experiments explored exogenous covert visual-attentional orienting following a brief peripheral cue. On each trial an attentional cue was followed by a stimulus in an empty field at 1 of 8 locations on an imaginary circle centered on the fixation point. The cued area size and the cue-target spatial relation were manipulated. Accuracy and response time were affected by the exogenous cue validity. Attention was allocated to a specific location in a visual quadrant: A target at an uncued location in a quadrant was not facilitated as much as target at the cued location, and a target in a different quadrant was inhibited in relation to a neutral condition. Cuing 2 locations in a quadrant was not as facilitative for targets at the cued locations or as inhibitive for targets at other locations compared with cuing a single location in a quadrant. Results are discussed in the context of several extent models of covert visual-spatial attention.