At any moment, the objects we face are endowed with a special behavioral status, either as potential obstacles during navigation or as optimal targets for visually guided actions. Yet, the gaze frequently jumps from one location to another when exploring the visual surroundings, so that objects located straight-ahead are often seen from the corner of the eyes. In the present study, we tested the hypothesis that peripheral vision might nevertheless ensure a privileged processing of these behaviorally important objects. Human subjects were asked to respond as fast as possible to the appearance of visual objects in their peripheral field of view while gazing successively in different directions. The visual objects formed similar images on the retina and differed only with respect to their egocentric location: either straight-ahead or eccentric with respect to the head/body midline. We found that straight-ahead objects elicit consistently shorter behavioral responses than eccentric objects (median difference of at least 10 ms). Additional experiments indicate that neither binocular visual cues nor full attentional resources play a fundamental role in this mechanism, and that it cannot be resumed to a simple preference for objects contralateral to the direction of gaze. These results are in agreement with recent electrophysiological findings showing that the early integration of gaze-related signals in the visual cortex of macaque monkeys lead to a higher neuronal sensitivity to the straight-ahead direction.

Ocular saccades bringing the gaze toward the straight-ahead direction (centripetal) exhibit higher dynamics than those steering the gaze away (centrifugal). This is generally explained by oculomotor determinants: centripetal saccades are more efficient because they pull the eyes back toward their primary orbital position. However, visual determinants might also be invoked: elements located straight-ahead trigger saccades more efficiently because they receive a privileged visual processing. Here, we addressed this issue by using both pro- and anti-saccade tasks in order to dissociate the centripetal/centrifugal directions of the saccades, from the straight-ahead/eccentric locations of the visual elements triggering those saccades. Twenty participants underwent alternating blocks of pro- and anti-saccades during which eye movements were recorded binocularly at 1 kHz. The results confirm that centripetal saccades are always executed faster than centrifugal ones, irrespective of whether the visual elements have straight-ahead or eccentric locations. However, by contrast, saccades triggered by elements located straight-ahead are consistently initiated more rapidly than those evoked by eccentric elements, irrespective of their centripetal or centrifugal direction. Importantly, this double dissociation reveals that the higher dynamics of centripetal pro-saccades stem from both oculomotor and visual determinants, which act respectively on the execution and initiation of ocular saccades.