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Saccadic peak velocity sensitivity to variations in mental workload.

INTRODUCTION
For research and applications in the field of (neuro)ergonomics, it is of increasing importance to have reliable methods for measuring mental workload. In the present study we examined the hypothesis that saccadic eye movements can be used for an online assessment of mental workload.


METHODS
Saccadic main sequence (amplitude, duration and peak velocity) was used as a diagnostic measure of mental workload in a virtual driving task with three complexity levels. We tested 18 drivers in the SIRCA driving simulator while their eye movements were recorded. The Wickens' multiple resources model was used as theoretical framework. Changes in mental workload between the complexity levels were evaluated multidimensionally, using subjective rating, performance in a secondary task, and other behavioral indices.


RESULTS
Saccadic peak velocity decreased (7.2 visual degrees/s) as the mental workload increased, as measured by scores of mental workload test (15.2 scores) and the increase of the reaction time on the secondary task (46 ms).


DISCUSSION
Saccadic peak velocity is affected by variations in mental workload during ecologically valid tasks. We conclude that saccadic peak velocity could be a useful diagnostic index for the assessment of operators' mental workload and attentional state in hazardous environments.