When can spatial attention be deployed in the form of an annulus?

Can spatial attention be deployed as an annulus? Some studies have answered this question in the positive, others in the negative. We tested the hypothesis that annular deployment depends on the presence of a suitable structural framework to which attention can be anchored. To this end, we added a structural framework to the displays of a study that failed to find an annular distribution of attention. The targets were displayed in an annular region around a central stream of task-irrelevant distractors which captured attention and impaired target identification. This design was replicated in our No-Anchors condition. In the Anchors condition in Experiments 1 and 2, a square outline was displayed at each of the four possible target locations. Consistent with the idea that attention can be deployed as an annulus only when a visual framework is present, the targets were identified more accurately (Experiment 1) and more rapidly (Experiment 2) when anchors were present than when they were absent. The number of anchors was increased to eight in Experiment 3. In Experiment 4 the central stream was omitted to verify that the enhanced performance did not arise from intrinsic properties of the anchors themselves. In Experiment 5, targets were presented in a blank annular region delimited by two concentric circles, thus obviating the possibility that attention was deployed as four or eight separate foci in Experiments 2 and 3, respectively.