Date Published: November 24, 2009
Publisher: Public Library of Science
Author(s): Matt Craddock, Rebecca Lawson, Hans P. Op de Beeck. http://doi.org/10.1371/journal.pone.0008009
Abstract: A variety of similarities between visual and haptic object recognition suggests that the two modalities may share common representations. However, it is unclear whether such common representations preserve low-level perceptual features or whether transfer between vision and haptics is mediated by high-level, abstract representations. Two experiments used a sequential shape-matching task to examine the effects of size changes on unimodal and crossmodal visual and haptic object recognition. Participants felt or saw 3D plastic models of familiar objects. The two objects presented on a trial were either the same size or different sizes and were the same shape or different but similar shapes. Participants were told to ignore size changes and to match on shape alone. In Experiment 1, size changes on same-shape trials impaired performance similarly for both visual-to-visual and haptic-to-haptic shape matching. In Experiment 2, size changes impaired performance on both visual-to-haptic and haptic-to-visual shape matching and there was no interaction between the cost of size changes and direction of transfer. Together the unimodal and crossmodal matching results suggest that the same, size-specific perceptual representations underlie both visual and haptic object recognition, and indicate that crossmodal memory for objects must be at least partly based on common perceptual representations.
Partial Text: Visual object constancy is the ability to consistently identify objects despite wide variation in their appearance attributable to such causes as a change in orientation between viewing instances . Recent research has started to investigate the attainment of object constancy in haptic object recognition, and how haptic and visual object recognition compare. When compensating for changes of object orientation, similar overall patterns of performance to those observed in vision have been found in the haptic modality –. In Craddock and Lawson  we established that there are also similar costs of size changes for visual and haptic familiar object recognition. Here, we extend that research to examine whether size-sensitive representations are modality-specific or are shared across the visual and haptic modalities.
Together the two studies reported here tested unimodal (HH and VV) and crossmodal (HV and VH) sequential matching of 3D models of familiar objects. In all four conditions performance was better on same-size relative to size-change matches, indicating that the perceptual shape representations underlying visual and haptic object recognition are size-sensitive. These results extend our previous findings of size-sensitivity in 2D visual and 3D haptic object recognition .