Measuring the separate effects of practice and fatigue on eye movements during visual search

Two experiments were conducted to examine how time-ontask (i.e., practice and fatigue) influences eye movements during visual search. In Experiment 1, we examined how practice influences eye movements during an extended visual search task. Results replicate the findings that over the course of a visual search task, performance improves and fixation duration increases. Yet changes in fixation duration did not correlate with changes in search performance. In Experiment 2, we examined how fatigue influences eye movements during an extended visual search task. To manipulate fatigue, participants either did or did not receive breaks. Those who did not receive breaks replicated the findings in Experiment 1. Critically, participants who did receive breaks showed no increase in fixation duration over the course of the visual search task. These results indicate that the increase in fixation duration with time-on-task reflects fatigue, and that this measure of fatigue can be derived independent of measures of performance improvements, such as shorter response times.