Abstract
Neurophysiological and psychophysical studies established that objects are a unit of attentional selection at early stages of visual processing. Behavioral evidence for object-based selection comes from attentional cueing studies, in which cueing a specific object increases an observers’ ability to detect and rapidly report a probe presented on the same object as compared to a different object (i.e., a same-object advantage). Here, we tested whether object-based attention is reflected in the speed and accuracy of saccadic eye movements executed within or across objects. We presented two C-shaped objects, located on an imaginary circle with an eccentricity of 3, 5, or 7 degrees of visual angle from the initial fixation point. We made the two shapes perceptually distinct using different textures and colored outlines. The shapes also appeared at different time points and moved along pseudo-random trajectories from different edges of the screen to their final positions (randomly oriented but opposite each other). Four saccade targets were located equidistantly at the ends of the two objects. A central cue pointed to one of the targets, instructing observers to make a sequence of two eye movements: A first saccade to the cued target, and a second saccade to the next target in the clockwise or counterclockwise direction (the direction remained constant within, but was balanced across, individuals). We varied cued locations and objects orientations such that observers made approximately the same number of second saccades within the same and to the different object. Comparing second saccade characteristics in the same vs. different object conditions, we found that — across all object eccentricities — second saccades within the same object had shorter latencies and had more accurate landing positions than second saccades to a target located on a different object. These findings suggest that that object-based attention contributes to saccade preparation and execution