Different computations underlie overt and covert spatial attention

Abstract

Perception and action are tightly coupled: visual responses at the saccade target are enhanced right before saccade onset. This phenomenon, presaccadic attention, is a form of overt attention--deployment of visual attention with concurrent eye movements. Presaccadic attention is well-documented, but its underlying computational process remains unknown. This is in stark contrast with covert attention--deployment of visual attention without concurrent eye movements--for which the computational process is well characterized. Here, a series of psychophysical experiments reveal that presaccadic attention modulates visual performance only via response gain changes even when attention field size increases, violating the predictions of a normalization model of attention, which has been widely used to explain the computations underlying covert attention. Our empirical results and model comparisons reveal that the perceptual modulations by overt and covert spatial attention are mediated through different computations.