Eye movements during parallel-serial visual search

Two experiments (one using O and Q-like stimuli and the other using colored-oriented bars) investigated the oculomotor behavior accompanying parallel-serial visual search. Eye movements were recorded as participants searched for a target in 5- or 17-item displays. Results indicated the presence of parallel-serial search dichotomies and 2:1 ratios of negative to positive slopes in the number of saccades initiated during both search tasks. This saccade number measure also correlated highly with search times, accounting for up to 67% of the reaction time (RT) variability. Weak correlations between fixation durations and RTs suggest that this oculomotor measure may be related more to stimulus factors than to search processes. A third experiment compared free-eye and fixed-eye searches and found a small RT advantage when eye movements were prevented. Together these findings suggest that parallel-serial search dichotomies are reflected in oculomotor behavior.