Working memory load is reflected in the frequency of microsaccades

Abstract

Microsaccades are tiny eye movements that individuals perform unconsciously during fixation. Despite the nature and the purpose of microsaccades are still lively debated, recent evidence showed an association between these micro eye movements and higher-order cognitive processes. In two experiments, here we specifically focused on working memory and addressed whether differential memory load could be reflected in a modulation of microsaccade dynamics. In Experiment 1, participants memorized a numerical sequence composed of either two (low-load condition) or five digits (high-load condition), appearing at fixation. The results showed a reduction in the microsaccadic rate in the high-load compared to the low-load condition. In Experiment 2, the numerical sequence was composed of five digits colored all in red or in green. Participants either memorized the five digits (high load) or the color (low load) of the numerical sequence. Hence, visual stimuli were exactly the same in both conditions. Consistent with Experiment 1, microsaccadic rate was lower in the high-load than in the low-load condition. Overall, these findings reveal the presence of a link between working memory and microsaccades.