Eye Movements as an Index of Mental Workload

Two investigations were carried out to assess the feasibility of using eye movement measures as nonintrusive indicants of mental workload. In the first experiment, measures of saccadic latency and eye movement velocity were obtained during alternating eye movement scans using an infrared tracking method and electro-oculographic techniques while subjects were differentially task loaded by simple moderate, and complex auditory tone counting. The latency and eye movement velocity measures changed but did not differ reliably as tone counting complexity (workload) was increased. In the second experiment, the spatial extent of spontaneous saccades was measured under three levels of tone counting complexity. The results indicated that the extent of such eye movements varied inversely (P less than .0151) as tone counting complexity increased. This indx appears to hold promise for the development of an objective indicator of mental workload. Keywords; Eye movement velocity; Saccadic latency; Saccadic extent; Mental workload; Human performance.