Effect of Gravito-Inertial Cues on the Coding of Orientation in Pre-Attentive Vision

Abstract

To see if the spatial reference frame used by pre-attentive vision is specified in a retino-centered frame or in a reference frame integrating visual and nonvisual information (vestibular and somatosensory), subjects were centrifuged in a nonpendular cabin and were asked to search for a target distinguishable from distractors by difference in orientation (Treisman’s “pop-out” paradigm [1]). In a control condition, in which subjects were sitting Immobilized but not centrifuged, this task gave an asymmetric search pattern: Search was rapid and pre-attentional except when the target was aligned with the horizontal retinal/head axis, in which case search was slow and attentional (2). Results using a centrifuge showed that slow/serial search patterns were obtained when the target was aligned with the subjective horizontal axis (and not with the horizontal retinal/head axis). These data suggest that a multisensory reference frame is used in pre-attentive vision. The results are interpreted in terms of Riccio and Stoffregen’s “ecological theory” of orientation in which the vertical and horizontal axes constitute independent reference frames (3).