Abstract
Numerous studies have demonstrated that sighted and blind individuals find it difficult to recognize two-dimensional tactile pictures of common objects. However, it is still not clear what makes recognition of tactile pictures so difficult. One possibility is that observers have difficulty acquiring global shape from haptic information when feeling the images. Alternatively, observers may have an accurate understanding of the shape but are unable to link it to a particular object representation. We conducted two experiments to determine where tactile picture recognition goes awry. In Experiment 1, we tested blindfolded sighted observers on their ability to recognize an array of tactile pictures. We then correlated recognition with image characteristics that influence shape perception and object naming. We found that recognition of tactile pictures correlated with image characteristics that affect shape acquisition (symmetry and complexity). In Experiment 2, we asked sighted drawing experts to draw their perception of the tactile pictures after feeling them. The drawing experts produced three types of drawings when they could not recognize the tactile pictures: 1) drawings that do not look like objects, 2) drawings that look like incorrect objects, and 3) drawings that look like the correct objects. The majority of errors reflected an inaccurate perception of the global shape of the image (error type 1). Our results suggest that recognition of simplistic tactile pictures of objects is primarily inhibited by low-level tactile shape processing rather than high-level object recognition mechanisms. Furthermore, instances of recognition failure even with accurate shape acquisition indicate that tactile information might be stored as chains of simple local features without the synthesis of a global gestalt.
Fight for Sight Postdoctoral Fellowship, James McDonnell Foundation grant.