The bimodality of saccade duration during the exploration of visual scenes

Eye movement parameters are consistently investigated, and the distribution of these parameters are well known. Whereas saccade duration has been studied along with saccade amplitude , the distribution of saccade duration has not yet been reported. We aim to investigate the distribution of saccade duration in several eye movement datasets from the literature and from our own data to confirm the common, but never reported, observation that the distribution of saccade duration is bimodal. We consistently observed the bimodality of saccade durations, not task- or stimuli-dependent. We created two groups of saccades based on the saccade duration distribution. Our results suggest that short duration saccades could be partly linked to bottom-up processes and long duration saccades to top-down processes. This study highlights the importance of reporting the distribution of eye movement data, in addition to means, which do not allow a correct and representative analysis in the case of bimodal distributions.