Abstract
Endogenous attention acts by enhancing sensory processing (perceptual sensitivity) and prioritizing gating of attended information for decisions (choice bias). It is unknown if the sensitivity and bias components of attention are under the control of common or distinct mechanisms. We tested human observers on a multialternative visuospatial attention task with probabilistic cues, whose predictive validity varied across locations. Analysis of behavior with a multidimensional signal detection model revealed striking dissociations between sensitivity and bias changes induced by cueing. While bias varied in a graded manner, reflecting cue validities, across locations, sensitivity varied in an ‘all-or-none’ fashion, being highest at the cued location. Cue-induced modulations of sensitivity and bias were uncorrelated within and across observers. Moreover, bias changes, rather than sensitivity changes, covaried robustly with key metrics of reaction times and optimal decision-making. Our results demonstrate that endogenous attention engages not a unitary process, but dissociable sensory and decisional processes.
