Differential sensitivity to surface curvature polarity in 3D objects is not modulated by stereo disparity

Cristino, Filipe, Davitt, Lina I., Rettie, Hannah and Leek, Elwyn (2015) Differential sensitivity to surface curvature polarity in 3D objects is not modulated by stereo disparity. Perception, 14, [1114]. (doi:10.1167/14.10.1114).

Abstract

It has previously been shown that observers are more sensitive to detecting changes in concave relative to convex curvature in the bounding contour of 2D shapes (e.g., Barenholtz et al., Cognition, 2003). Here we examined two related issues: (1) Whether this differential sensitivity to curvature polarity extends to the surfaces of three-dimensional (3D) objects, and (2) whether the detection of surface curvature polarity is modulated by stereo disparity. We created 3D rendered 'asteroid like' stimuli, keeping the silhouette constant but modifying part of the object surface by either introducing, removing, extending or reducing a new concave or convex region. In two separate experiments, we asked participants to discriminate between two sequentially presented 3D shapes under either mono or stereo viewing conditions. The results showed that, analogous to curvature detection in 2D bounding contour, participants are significantly better at discriminating between objects if changes occur in a concave region compared to a convex one. We also found observers to be significantly more accurate at detecting changes when curved regions were introduced or removed in comparison to when these were extended or reduced in magnitude. Surprisingly, we found no viewing condition effect; participants performed very similarly in all conditions when viewing the objects in either 2D or 3D, suggesting that the disparity cue is not used to perform the task. These findings provide further evidence of the functional status of concave regions in 3D shape representation.

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Contributors

Author: Elwyn Leek

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