Effect of size of attended area on contrast sensitivity function.

Contrast sensitivity functions (CSFs) were measured in the foveal region while subjects simultaneously performed an instantaneous judgment task, which was designed to maintain their attended areas at a constant size. Spatial attention was sustained over areas that were either narrow (Narrow condition) or broad (Broad condition). We observed that the sensitivity at higher frequencies (over 3 cpd) was greater under the Narrow condition than that under the Broad condition, supporting the argument that attention enhances spatial resolution.