A pupillary measure of forgetting: Memory interference is revealed by pupil size changes at retrieval

Pupil dilation is a reliable measure of cognitive load, and many studies have shown this effect in relation to various memory tasks. Interference from irrelevant memory traces encoded in the past lead to difficulty retrieving recent, sought after memory traces, and increased cognitive load. This investigation showed a significant decline in performance during buildup of interference and a significant improvement when interference was resolved. Significant differences in pupil size were observed when participants retrieved information, with increased pupil dilation during interference as compared to during resolved interference. The results reveal a relationship between inhibitory memory mechanisms and changes in pupil size, and show that pupillometry is a simple but sensitive physiological measure of memory interference