Abstract
Before actually looking at or reaching for an object, the focus of attention is first allocated to the object. Here we investigated whether the perceptual benefits produced by these pre-motor shifts of attention cumulate if an object is targeted by multiple effectors (eyes and hands). Participants were cued to move either gaze or a single hand (one effector), two hands or both gaze and a hand (two effectors), or gaze and two hands (three effectors) to objects in the periphery. These eight objects suddenly changed identity and one distinct object (the probe) needed to be discriminated before the actual initiation of the movements. The probed object was either targeted by none (cue invalid), or one or more effectors (cue valid). Results showed that average discrimination performance decreased linearly per additional effector independent of cue validity, but also linearly increased per additional cue-valid effector that targeted the probed object. Moving two hands to the probed object resulted in better recognition performance as compared to moving only gaze or one hand. These results have three implications: (1) the more complex the motor program, the worse the performance, (2) the more effectors planned to move to the yet-to-appear object, the more attentional resources it receives and the better it is perceived, and (3) the cumulation of perceptual benefits points at parallel and presumably independent mechanisms that evoke pre-motor shifts of attention. We speculate that recognition may improve even further when more effectors (e.g., feet, posture, or head movements) are moved to objects.