Abstract
Concurrent working memory tasks can degrade search efficiency when they are spatial in nature or require central executive processing (Woodman & Luck, 2004; Oh & Kim, 2004; Han & Kim, 2004). We investigated the role of executive functioning in visual search by tracking the eyes of subjects while they performed a concurrent auditory working memory task. The secondary auditory task required subjects to keep track of two tones: a sine and square wave with the same fundamental frequency presented monaurally. The tones occurred at pseudo-random intervals, and a staircase method was used to adjust the delay between the tones so that accuracy on the secondary tone task was around 80%. Response times and error rates for the search task were higher in the dual-task condition compared to the search-only condition, indicating that the secondary task interfered with visual search. The longer response times were not due to increased gaze durations, but rather to an increased number of gazes. In the dual-task condition, subjects were more likely to examine a target and then continue searching, suggesting that the secondary task caused subjects to suffer from inattentional blindness. However, an analysis of gaze durations indicates that this inattentional blindness is the result of an inability to inhibit queued shifts of attention. That is, occupying executive control caused shifts of attention to be executed before item processing was complete, which led to the increased number of gazes in the task. Executive control appears to be directly tied into this inhibition process.