Facilitation and inhibition mechanisms of human visuospatial attention in a non-search task.

This study investigated both facilitation and inhibition mechanisms of attentional orienting. Orienting consists in shifting the attentional focus in the visual field. To study the distribution of attentional resources, a two-choice-reaction time task with compatible and incompatible flankers was used. When an irrelevant flanker is presented adjacent to a target stimulus, interference is observed when the two stimuli are associated with conflicting responses (flanker effect). Orienting of attention, at cued and uncued flanker locations, was manipulated by an exogenous cueing paradigm (automatic capture following a peripheral visual transient). Results showed that orienting of attention at cued distractor location produces an increased flanker effect as compared to the no-cue condition. In contrast, the flanker effect was absent when the attentional focus shifted to the uncued distractor location. These effects were interpreted in terms of facilitation and inhibition processes of visuospatial selection by early attentional competition models.