Where did I come from? Where am I going? Functional differences in visual search fixation duration.

Real time simulation of visual search behavior can occur only if the control of fixation durations is sufficiently understood. Visual search studies have typically confounded pre- and post-saccadic influences on fixation duration. In the present study, pre- and post-saccadic influences on fixation durations were compared by considering saccade direction. Novel use of a gaze-contingent moving obstructer paradigm also addressed relative contributions of both influences to total fixation duration. As a function of saccade direction, pre-saccadic fixation durations exhibited a different pattern from post-saccadic fixation durations. Post-saccadic fixations were also more strongly influenced by peripheral obstruction than pre-saccadic fixation durations. This suggests that post-saccadic influences may contribute more to fixation durations than pre-saccadic influences. Together, the results demonstrate that it is insufficient to model the control of visual search fixation durations without consideration of pre- and post-saccadic influences.