UC Riverside

Spatial attention is a mechanism by which observers are able to enhance the processing of information at relevant locations. Spotlight, zoom lens, and gradient theories of attention make no predictions about how spatial attention is directed in three-dimensional (3D) scenes. This is an oversight, because previous research has demonstrated that younger and older observers can direct their attention in depth. However, previous experiments on the topic of spatial attention for 3D scenes have been conducted using stimuli that are not typical during real-world task performance or have failed to provide compelling controls for potential confounding variables that are two-dimensional (2D). Therefore, it is uncertain whether younger and older observers can direct their attention in depth during real-world task performance. To address these limitations, I conducted experiments to test the hypothesis that spatial attention is based on a 3D representation of the scene. Several predictions are proposed based on this hypothesis. First, that the allocation of attention in depth is not a consequence of the projected size or 2D spatial separation of the targets but due to their perceived position in depth. Second, that 3D spatial attention will occur for stimuli that do not include binocular disparity as a source of depth information. Third, that 3D spatial attention effects will not be dependent on eye fixation. Lastly, that 3D spatial effects will occur with different tasks. Following from previous research, I also hypothesize that the spatial extent of attention is reduced for older individuals as compared to younger individuals. If these hypotheses are correct, then there will be a reduction in spatial attention along the axis of depth for older individuals as compared to younger individuals. In these experiments, younger and older drivers performed a light detection task and one of two car-following tasks in a simulator lacking binocular disparity information for depth. The results from these experiments were consistent with the predictions of the 3D spatial attention hypothesis. Although there were age-related differences in spatial attention, a reduction in spatial attention along the axis of depth for older individuals was not observed.