Attentional competition across saccadic eye movements

Abstract

Human behavior is guided by visual object recognition. For being recognized, objects compete for limited attentional processing resources. The more objects compete, the lower is performance in recognizing each individual object. Here, we ask whether this competition is confined to eye fixations, periods of relatively stable gaze, or whether it extends from one fixation to the next, across saccadic eye movements. Participants made saccades to a peripheral saccade target. After the saccade, a letter was briefly presented within the saccade target and terminated by a mask. Object recognition of the letter was assessed as participants' report. Critically, either no, two, or four additional non-target objects appeared before the saccade. In Experiment 1, presaccadic non-targets were task-irrelevant and had no effects on postsaccadic object recognition. In Experiment 2, presaccadic non-targets were task-relevant and, here, postsaccadic object recognition deteriorated with increasing number of presaccadic non-targets. As suggested by Experiment 3 and a mathematical model, this effect was due to a slowing down but also a delayed start of visual processing after the saccade. Together, our findings show that objects compete for recognition across saccades, but only if they are task-relevant. This reveals an attentional mechanism of task-driven object recognition that is interlaced with active saccade-mediated vision.