Time on task and blink effects on saccade duration.

Changes in saccade duration, saccade amplitude and slope of the regression line relating amplitude and duration were assessed during a 2 hour air traffic control simulating task. Mean duration significantly increased as a function of time on task (TOT). Saccade amplitude decreased during the beginning part of the two hour period, increased in the middle and decreased in the final part of task performance. Differences in saccade duration were also assessed for saccades occurring during and independent of eye blinks. When matched for amplitude, electrooculographically measured saccades occurring during a blink were significantly slower than those occurring independent of a blink. Our results suggest caution in interpreting saccade velocity change as an index of 'fatigue' since most of the reduction in average saccade velocity may be secondary to increases in blink frequency.