Initial saccades predict manual recognition choices in the monkey

Abstract

In animals with specialized foveae, eye position has a direct influence over the acquisition of detailed visual information. At the same time, eye movements executed during natural behaviors are closely linked with motor actions. In this study, we investigated patterns of eye movements during a simple visual discrimination task. Three rhesus monkeys learned to recognize images of real world objects with no explicit constraints on eye position. Analysis of the monkeys’ eye movements showed that although the endpoint of the initial saccade depended on the particular visual stimulus, the trajectory of the first saccades also reliably predicted the manual response associated with that stimulus. We thus observed that initial saccades executed in a recognition task reflect both perceptual and motor aspects of a visual task. This pattern of eye movements emerged spontaneously in all three animals tested despite the fact that saccades were never explicitly rewarded. As the average saccade latency was under 200 ms, object specific learned associations must have exerted their influence over the initial saccade even earlier, providing a novel temporal marker for the rapidity of visual recognition processes. Taken together, these results suggest that caution should be exercised when interpreting the meaning of oculomotor patterns observed during perceptual tasks, as these blur the line between perceptual processing and motor preparation.