Abstract
This study examined a method to objectively quantify cognitive workload using eye movement patterns. Participants' eye movements were recorded every 20 milliseconds while participants fixated the center of a computer monitor. For the first 8 seconds of each experimental block, a red dot indicated the center of the computer screen and then disappeared. The participants were instructed to keep their fixation in the center of the screen after the center red dot disappeared. While fixating, participants performed one of three secondary tasks designed to systematically vary the participants' mental workload. The three secondary tasks consisted of a Simple Reaction Task, and two levels of an auditory “n-back” task (i.e., 1 and 3 back). The auditory stimuli were random numbers between one and four. The numbers were presented one every 2.5 seconds. Participants indicated their response to the secondary tasks by pressing a button. Saccadic eye movements irrelevant to the task were found to increase in response to the increased mental workload. The saccadic eye movements were calculated by taking the moving average of the gap between the current fixation point (that was the average of the recent 400 milliseconds) and the previous fixation point (the average of another 400 milliseconds). The pattern of saccadic eye movements were correlated (R2=.86) with pupil size dilation which has also been shown to systematically vary with mental workload. The results suggest that mental workload may be objectively quantified by observing the pattern of saccadic eye movements.
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