November 1969
The Perception of a Permanent World
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 References to these essays must cite them explicitly as unpublished manuscripts.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 sensations that accompany perception are ever-changing, fleeting, transient (temporary) whereas the percepts themselves are enduring, recurrent, persisting under change (permanent).
2. The theory of sensation-based perception must assume that this phenomenal permanence is a contribution of the observer. The “concept” of object-permanence is imposed on the data of sense. So theorists like Kant and Piaget assert. It is taken for granted that awareness of a hidden object or an object behind one’s back can only be an idea or a memory-image, since it is not sensory. This is a common assumption for both nativism and empiricism. Awareness of such an object must come from the brain since it cannot come from the light entering the eye.
3. The theory of perception based on the notion of the available information in ambient light and on the assumption that an observer samples this information is quite different. It starts with points of observation with projected and unprojected surfaces at each point of observation (those hidden and those not hidden, respectively) and with the possibility of head-turning at each point of observation. It assumes that when an object goes “out of sight” the fact of its continuing existence is specified (Gibson, Reynolds, Wheeler, & Kaplan).
4. Can experiments on the so-called “delayed-reaction” (Zuckerman) be interpreted as showing that animals detect the continued existence of a food-object after it has been occluded (covered up, hidden)?
5. Can Michotte’s “tunnel phenomenon” and the “rabbit-hole phenomenon” be interpreted in the same way, and also the recent results with animals and babies on behavior towards hidden objects?
6. Does the evidence about “cognitive maps” in the maze-learning of rats, and the homing-behavior of animals, show that they orient to objects and places that are not projected in the field of view, or in the retinal image?
7. How does Gibson’s theory of the visual feedback from locomotion apply to the perceiving of places that have gone out of sight? First to consider is the “opening up” and “closing away” of the “vistas” of the world of occlusion. Second, there is the magnification and minification of figures in the array by approach and withdrawal (motion perspective). These transitions and these transformations are reversible; in fact they are reversed whenever an observer returns to a place from which he started. I believe we should think of this fact not as the recurrence of a “stimulus” but as the canceling out of a change.
8. When an object goes out of existence instead of going out of sight the corresponding optical change does not in fact reverse and nothing an observer can do will make it reverse, except to run a film of the event backwards. (This might be called Humpty-Dumpty transformation.) Group theory in mathematics seems to apply to reversible transformations, but what theory is applicable to a non-reversible transformation?
9. The phenomenal constancy of the size and the shape of a moving object is usually complete, that is, the experiment of observing size with changing distance or shape with changing slant (e.g. Gibson & Gibson) yields simple perceptions instead of the complicated judgments that the static consistency does. In this case, the invariances of perception despite varying sensations (retinal images) can be ascribed to a mathematical invariant in the stimulus flux. The hypothesis of variance under transformation leads to the idea of the phenomenal rigidity of moving objects and surfaces.
10. What connection, if any, is there between the hypothesis of invariance under transformation for explaining phenomenal rigidity and the hypothesis of persistence underlying change for explaining phenomenal permanence? If the flowing array of ambient stimulus energy is just that (and not a sequence of “stimuli”) what is it that persists? And what does that reversibility of certain kinds of change have to do with it?