Allocation of Attention in Three-Dimensional Space

Experiments examining shifts of attention in visual space have used largely two-dimensional representations of visual space. However, the representation of depth is of particular importance for the visual system of an active human observer, so the operation of attention in depth must also be considered. While early work was equivocal with regard to the operation of attention in depth, the present review of recent research suggests that spatial visual attention has a depth component. There is a cost for switching attention between discrete locations in depth under most conditions. Across the life span, the human attention system is generally able to attend to a region in depth selectively and to use depth to guide attentional selection of objects. Exceptions to these costs and unresolved issues are also reviewed.