ATTENTION SHUTS OUT IRRELEVANT STIMULI

Express saccade experiments imply that attention shifts take time. We extend this result with new experiments on manual reaction times. Reac tion to a cued target is always slower than reaction to an uncued cont rol, even when the cue is correct, if control trials are blocked to pr event interference from cued trials. Attention functions not to speed response, but to prevent responses at irrelevant locations.