Abstract
Concepts like the span of the effective stimulus or the functional visual field (FVF) have been increasingly investigated in recent visual search and eye tracking studies. In particular, the FVF has been used to explain how many fixations are necessary to find a target and why observers sometimes miss a target even though their gaze fell close to the target position. FVF studies usually focus on the number of fixations or on saccade amplitude. In contrast, fixation durations received very little attention in the literature and are often assumed not to vary in a meaningful manner as a function of the current visual input. In the present study, we assume that the presence of the target within the FVF can speed saccade planning and that this registers in shorter fixation durations before a saccade is made to the target. We conducted a free viewing search experiment where participants had to find a specific target shape. Results showed shorter fixation durations for the last distractor fixation before a saccade was directed to the target. Fixation durations are not shorter when target discriminability is low, suggesting that the subsequent target saccade is not guided by target information. Moreover, shorter fixation durations only occur when the fixation is within a specific distance to the target. We discuss whether fixation durations are only shortened by facilitated saccade planning when the target falls within the functional visual field. If so, fixation durations could be used to estimate the size of the functional visual field or the span of the effective stimulus.