Abstract
Introduction: Previous research has suggested that changes in pupil diameter reflect mental effort in verbal short-term memory tasks, dilating with increases in memory load and constricting during recall (Kahneman & Beatty, 1966, Science). We sought to describe the relationship between mental effort and performance in a visual short-term memory task using pupillometry. We predicted that greater pupil dilation (more mental effort) during encoding and/or maintenance correlates with higher performance. Method: Participants performed an object recognition task, where on each trial two computer-generated scenes were presented to the left and right of central fixation. Each scene contained six target objects. A visual cue prior to the presentation of the scene instructed participants which scene to attend to, allowing them to search the scene for the objects. Attention was controlled by varying cue reliability (100%, 75%, and 50%). After a three second delay, participants were probed about a single object, indicating whether it was present or not in the scene. For each response, participants also rated their confidence level. Eye gaze data and pupil diameter was collected using a Tobii T120 eye tracker. Results: Performance (correct recall) was greater for the 100% reliable cue condition compared to the 75% and 50% conditions and participants reported greater confidence in their responses in the 100% condition. The magnitude of pupil dilation during the delay period tended to be greater for correct than incorrect responses. Conclusion: These findings provide further support that pupillometry is a powerful and sensitive index of mental effort in visual memory tasks. Greater effort during memory maintenance predicts better performance in visual short-term memory tasks.
Meeting abstract presented at VSS 2014