November 1970
Inquiry into Sensations
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 References to these essays must cite them explicitly as unpublished manuscripts.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.
Consider the following assertions. Are they decreasingly obvious?
1. We do not usually perceive light, we perceive things and events by means of light (activity of looking). What about the perceiving of “light”?
2. We do not usually perceive sounds, we perceive events by means of sound, i.e., mechanical or vibratory events by means of pressure-waves. (Activity of listening.)
3. We do not usually perceive touches (skin deformations), we perceive objects and events by means of touch (activity of touching). Under what conditions do we perceive touches?
4. We do not usually perceive tastes, we perceive substances (in the mouth) by means of taste (activity of tasting).
5. We do not ever usually perceive smells, we perceive volatile substances in the air, and their sources in the world, by means of smell (activity of smelling or sniffing).
In each case we can experience a “sensation,” (i.e., a “mere impression”) of light, of sound, of touch, of taste, and of smell. Are they increasingly obvious in this list? Why?
What general conditions make sensations obvious, obtrusive, or easier to experience? Here are nine suggestions. What others can be made?
1. Passivity of the observer. I.e., the imposition of stimulation instead of obtaining it (e.g., fixed head and eyes, the tachistoscope; use of headphones; fixed limbs; olfactometer).
2. Failure to explore (look around, harken or turn the head, actively touch, savor, sniff or face the wind). Failure to detect invariance under change.
3. The impossibility of exploration (e.g., the objects in the night sky).
4. Preoccupation with the body as a source of stimulation (introspection, introversion, and mental disease; hallucination). A “subjective” attitude.
5. Rapidly changing imposed stimulation; succession too fast for perceptual adjustment.
6. Prolonged stimulation (afterimages) and intense stimulation (dazzle, pain). “Noxious” stimuli.
7. Encountering things not previously experienced, without opportunity for perceptual learning. The situation of the infant?
8. Conflicting or equivocal stimulus invariants (information or “cues” for objects that could not coexist).
9. Internal or direct stimulation of the nervous system (electrical stimulation, diseases, desynchronization of neural circuits).
Is it true that the conditions that make sensations obtrusive are the very conditions that make perception deficient?
Is it true that so-called “sensory deprivation” is actually a situation that enhances the experience of sensations?
What is the reason for studying the arousal of sensations in the laboratory (psychophysics)?