Depth cue combination in spontaneous eye movements

Abstract

Where we look when we scan visual scenes is an old question that continues to inspire both fundamental and applied research. Recently, it has been reported that depth is an important variable in driving eye movements: the directions of spontaneous saccades tend to follow depth gradients, or, equivalently, surface tilts (L. Jansen, S. Onat, & P. König, 2009; M. Wexler & N. Ouarti, 2008). This has been found to hold for both simple and complex scenes and for a variety of depth cues. However, it is not known whether saccades are aligned with individual depth cues, or with a combination of depth cues. If saccades do follow a combination of depth cues, then it is interesting to ask whether this combination follows the same rules as the well-studied case of depth cue combination in conscious perception. We showed subjects surfaces inclined in depth, in which perspective and binocular disparity cues specified different plane orientations, with different degrees of both small and large conflict between the two sets of cues. We recorded subjects' spontaneous saccades while they scanned the scene, as well as their reports of perceived plane orientation. We found that distributions of spontaneous saccade directions followed the same pattern of depth cue combination as perceived surface orientation: a weighted linear combination of cues for small conflicts, and cue dominance for large conflicts. The weights assigned to the cues varied considerably from one subject to the next but were strongly correlated for saccades and perception; moreover, for both perception and saccades, cue weights could be modified by manipulating cue reliability in a way compatible with Bayesian theories of optimal cue combination. We also measured vergence, which allowed us to calculate the orientation of the plane fitted to points scanned in depth. Contrary to perception and saccades, vergence was dominated by a single cue, binocular disparity.

Computational Model of Stereoscopic 3D Visual Saliency

“…Wismeijer et al [28] examined if saccades were aligned either with individual depth cues or with a combination of depth cues, by presenting stimuli in which monocular perspective cues and binocular disparity cues conflicted. Their results indicate a weighted linear combination of cues when the conflicts are small, and a cue dominance when the conflicts are large.…”

Stereo Disparity Facilitates View Generalization during Shape Recognition for Solid Multipart Objects

“…Stereo viewing enhances specific kinds of shape information about local surface depth orientation and curvature minima arising at part boundaries (Norman et al, 1995;Welchman et al, 2005;Wismeijer et al, 2010). We predicted that under structural description approaches which assume high-level part segmentation the availability of this information under conditions of stereo viewing should facilitate recognition and view generalisation (e.g., Biederman 1987;Hoffman & Richards, 1984;Hummel & Stankiewicz, 1996;Marr & Nishihara, 1978;Leek et al, 2005;Leek et al, 2009).…”

Perceptual Organization and Consciousness

“…For example, subtle eye movements may change the retinal projection of the Necker cube and favour one interpretation of the two-dimensional image over another (Einhäuser et al 2004). In this context it is also worth noting that eye movements do not correspond with perceived depth of a stimulus but reflect lowlevel attributes of the image (Wismeijer et al 2008(Wismeijer et al , 2010. For ambiguous structure-from-motion stimuli that lead to perception of a three dimensional shape spinning either clockwise or anti-clockwise, the percept may depend on whether attention is directed to the dots drifting to the left or to the right.…”