Does Cognitive Load Affect Eye Movements/Oculomotor Behavior in Natural Scenes?

Abstract

Cognitive neuroscience researchers have identified relationships between cognitive load and eye movement behavior that are consistent with oculomotor biomarkers for neurological disorders. We develop an adaptive visual search paradigm that manipulates task difficulty and examine the effect of cognitive load on oculomotor behavior in healthy young adults. Participants (N=30) free-viewed a sequence of 100 natural scenes for 10 seconds each, while their eye movements were recorded. After each image, participants completed a 4 alternative forced choice task in which they selected a target object from the previously viewed scene, among 3 distracters of the same object type but from alternate scenes. Following two correct responses, the target object was selected from an image increasingly farther back (N-back) in the image stream; following an incorrect response, N decreased by 1. N-back thus quantifies and individualizes cognitive load. The results show that response latencies increased as N-back increased, and pupil diameter increased with N-back, before decreasing at very high N-back. These findings are consistent with previous studies and confirm that this paradigm was successful in actively engaging working memory, and successfully adapts task difficulty to individual subject’s skill levels. We hypothesized that oculomotor behavior would covary with cognitive load. However, there were no significant differences between the number or duration of fixations and saccades for high/low performing subjects, or between high/low performing trials for a given subject. Similarly, oculomotor behavior did not act as a predictor of correct/incorrect responses with increasing demand from the N-back task. Similarly, the proportion of each scene viewed was not related to N-back and was not a significant predictor of accuracy. These results suggest that cognitive load can be tracked with an adaptive visual search task, but that oculomotor strategies generally do not change as a result of greater cognitive demand in healthy adults.