November 1978
Memo on Vision and Touch Considered as Perceptual Systems
J. J. Gibson, Cornell University
The World Wide Web distribution of James Gibson’s “Purple Perils” is for scholarly use with the understanding that Gibson did not intend them for publication. References to these essays must cite them explicitly as unpublished manuscripts. Copies may be circulated if this statement is included on each copy.
1. The senses considered as channels of afferent input can be said to provide signals but they do not provide information as I use the term.
2. Information about the same reality is the same information, whatever system (sense) picks it up.
3. In ordinary perception, vision and touch can pick up the same information and manifest different sensory qualities. If looking and feeling co-operate there is extra assurance of perception, but this is not expressed by saying that there is “redundant information” for perception. Adults can learn to pay attention to the type of receptors excited, but the evidence suggests to me that infants pay no attention whatever to the receptors.
4. Concomitant stimulation of the photoreceptors and the mechanoreceptors is sought for but not always obtained. Looking and feeling can occur in isolation. And even when they covary, the different modes of energy can make a difference. Although one can both feel and see the texture of a surface, and the layout of a surface, one cannot feel the reflectance of a surface and one cannot see the temperature of a surface. The overlap in information pickup is not complete. But this fact is not to be confused with the specialization of receptors for modes of energy, and the “specific qualities of the nerves”, so-called, of Johannes Muller.
5. By various artificial methods the information available to the visual system can be made discrepant with the information available to the haptic system. The percept is usually in accordance with the visual information, that is, misperception occurs. The theory of pickup implies that nothing can be learned from such experiments. The situation is describes as one of conflicting information (or contradictory or inconsistent information, etc.) but these terms are inappropriate, being borrowed from language (predication). Discrepancy of information between perceptual systems, or within the visual system (as with ambiguous and reversible figures, that is, pictures) is not at all the same as discrepancy of verbal information.
The notion that one channel of input (sense) can validate the information of another, or serve to calibrate another is both theoretically confused and empirically wrong. Nothing can be done to bare sense data that will convert them into perceptions of the environment. Any theory of perceptual development that begins with independent sense perceptions must beg the question (Cf., Ch. 14 in The Ecological Approach).