Attention is the mechanism that allows us to select relevant information for processing from the vast [Page 91]amount of stimuli we are confronted with, prioritizing some while ignoring others. Attention can affect perception by altering performance—how well we perform on a given task—or by altering appearance—our subjective experience of a stimulus or object. Visual attention is commonly divided into three types: (1) spatial attention, which can be overt, when an observer moves his or her eyes to a relevant location and the focus of attention coincides with the movement of the eyes, or covert, when attention is deployed to relevant locations without accompanying eye movements; (2) feature-based attention, which is deployed to specific features (e.g., color, orientation or motion direction) of objects in the environment, ...