Exploring the Dissociations between Overt and Covert Mechanisms of Spatial Attention and Inhibition of Return

Abstract

Prompted by oculomotor theories of attention, the present experiments explore the role of saccade activation in the generation of two cueing effects: exogenous capture (Experiment 1) and inhibition of return (IOR; Experiment 2). Exogenous capture is shortlived and marked by faster responding toward recently stimulated locations, whereas the longer-lasting IOR manifests as slower responding toward those locations. Within each experiment, Group A performed in a dual-task in which on most trials a peripheral target had to be identified but infrequently a central arrow probe called for an eye movement instead, while for Group B the tasks were the same except saccade trials were frequent and target identification trials were infrequent. In Experiment 1, for group A uninformative cues captured attention as measured by faster digit identification at the cued location, an effect not accompanied by saccade activation. For group B, cues generated saccade activation without capturing attention. Thus saccade activation need not accompany exogenous covert capture, and covert capture need not accompany saccade activation. In Experiment 2, group A exhibited IOR which slowed digit identification, but did not affect saccadic responding, while Group B exhibited no IOR in either digit identification or eye movement trials. This finding provides converging evidence that IOR can be dichotomized into two forms; one which delays motor production itself (Evidenced amply elsewhere, e.g., Taylor & Klein, 2000) and another which delays responding by applying inhibition at a perceptual-motor interface which can operate in independence from its motoric cousin.