Abstract
Spatial attention can be flexibly changed to optimize visual processing. It can, for example, be moved from one location to another via a three-step process of disengaging, shifting, and engaging attention (attentional orienting) or it can be expanded or contracted in spatial extent to match the size of an attended object (attentional resizing). Although much is known individually about these aspects of attentional control, relatively little is known about how they interact with one another. In the present study we examined whether the spatial extent of the attentional focus modulates the efficiency of the first component of attentional orienting, the disengagement of attention. To test this, we used a small or large abrupt-onset central square to trigger the reflexive resizing of attention (Castiello & Umiltà, 1990) and a gap task to assess the rate of attentional disengagement (Mackeben & Nakayama, 1993). In the gap task, observers were cued to orient attention to a peripheral location. Prior to the onset of the orienting cue, the central fixation cross either disappeared (Gap condition) or remained visible (No-Gap condition). The removal of the fixation cross allowed attention to be disengaged early in the Gap condition, but not in the No-Gap condition. The task was to make a speeded discrimination response to a target. The rate of attentional disengagement can be estimated by subtracting average RT in the Gap condition from that in the No-Gap condition, and this RT difference is known as the gap effect. The results showed clearly that the magnitude of the gap effect was significantly greater when the focus of attention was small than when it was large (51.4 ms and 26.6 ms, respectively), indicating that the rate of disengagement was significantly slower when the focus of attention was small.