Inhibition of return spreads across 3-D space.

Focusing attention to a location in 3-D space operates much the same as in 2-D space. Attending a location in 2-D space is followed by a selective inhibitory aftereffect known as inhibition of return (IOR). Here, we report the results of two 3-D reflexive cuing studies in which depth was defined by binocular disparity. As has been shown before, attentional cuing was specific for x-y-z locations. However, the present results show that IOR is not depth specific. After a specific location in x-y-z is cued, IOR occurs for the depth plane in front of and behind the cued location. The finding that IOR spreads across depth planes may be related to how inhibited locations are encoded in the superior colliculus. We argue that the functional role of a depth-blind IOR is to bias attention against going back to any part of a previously attended object.