Perception of shapes is possible by touch and by sight. Kim and Zatorre have been using a coding of shape information into sound information to examine the nature of shape perception. They use boards with 2D drawings on them have textured surfaces giving visual and tactile targets. These are coded to give matching ‘soundscapes’ where one dimension is coded by frequency and the other by stereo panning. With current and previous experiments, they show that subjects can be trained to identify both visual and tactile targets from soundscapes. Further subjects trained to match sound and touch can do the matching of sight and sound without further training.
Here is the abstract:
Shape is an inherent property of objects existing in both vision and touch but not audition. Can shape then be represented by sound artificially? It has previously been shown that sound can convey visual information by means of image-to-sound coding, by whether sound can code tactile information is not clear. Blindfolded sighted individuals were trained to recognize tactile spatial information using sounds mapped from abstract shapes. After training, subjects were able to match auditory input to novel auditory-tactile pairings. Furthermore, they showed complete transfer to novel visual shapes, despite the fact that training did not involve any visual exposure. In addition, we found enhanced tactile acuity specific to the training stimuli. The present study demonstrates that as long as tactile space is coded in a systematic way, shape can be conveyed via a medium that is not spatial, suggesting a metamodal representation.
Not mentioned in the abstract is their theory of what these experiments say about the perception of shapes.
This transfer of crossmodal learning further supports our hypothesis that shape can be represented at a highly abstract level in a form independent of the sensory modality in which it is learned. This amodal, abstract representation of shape is closely associated with the findings of human imaging studies that identified the lateral occipital region as a common brain region involved in shape recognition by both vision and touch and by audition using the same type of sound transformation used in the current study.
It is interesting to think of shape perception as a link between two aspect of perception: the housing of our perceptions in a three dimensional space and the separation of our perceptions into distinct objects. Both of these seem hardwired and at the foundation of the form our conscious awareness takes.
Kim, J., & Zatorre, R. (2010). Can you hear shapes you touch? Experimental Brain Research, 202 (4), 747-754 DOI: 10.1007/s00221-010-2178-6