Eye movements in visual fixation predict behavioral response performance in sustained attention

Individuals naturally make eye movements over time during visual fixation and voluntarily perform changes in eye position. However, the functional implication of spontaneous changes of eye movements remains unclear. Given that visual fixation is commonly used as a baseline condition in cognitive experiments, we conducted an experiment using eye-tracking to test whether spontaneous fluctuations in eye position are linked to sustained attention. Eye-position data were collected while subjects performed visual fixation and a sustained attention task. We found that slow fluctuations (<0.2 Hz) in eye position correlated with slow fluctuations in response behavior [reaction time (RT)] during the sustained attention task. Further analysis revealed that off-task but not on-task slow fluctuations in eye position contributed to slow fluctuations in sustained attention behavior. The spontaneous fluctuations in eye position could predict the behavioral performance in sustained attention. These results provide new insights into the functional significance of eye movements during visual fixation, which should be considered in interpreting the findings of cognitive experiments using visual fixation as the baseline condition.