Abstract
Most investigations of object recognition have focused on the form rather than the material properties of objects. Nevertheless, knowledge of the material properties of an object (via its surface cues) can provide important information about that object's identity. In this study, we used Garner's speeded-classification task to explore whether or not the processing of form and the processing of surface properties are independent. In an initial form task, participants made length and width classifications. Participants were unable to ignore length while making width classifications, and were unable to ignore width while making length classifications. This suggests that length and width, which are two cues to object form, share common processing resources. In a subsequent surface-property task, participants made texture and colour classifications. Participants were unable to ignore colour while making texture classifications, and were unable to ignore texture while making colour classifications. This result in turn suggests that texture and colour, which are two characteristics of an object's surface, share common processing resources. Finally, in a combined task, we directly examined possible interactions between the processing of form and the processing of surface properties. In contrast to the findings with the other two tasks, participants were able to ignore form while making surface-property classifications, and to ignore surface properties while making form classifications. These behavioural results converge nicely with neuroimaging studies (Cant et al. VSS 04 & 05) showing that the form of objects and their surface properties are processed by relatively independent neural mechanisms.
Authors J.S.C. and M.E.L. contributed equally to this research. Supported by a grant from Canadian Institutes of Health Research to M.A.G.