December 1968

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 References to these essays must cite them explicitly as unpublished manuscripts.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.

It seems to be the accepted idea that the puzzle of the retinal image consists only of the fact that it is inverted relative to the object, whereas the perception is "upright" (Stratton) and it is further agreed that, in our sophistication about the nervous system, the puzzle is now solved. The solution is that the connections of the neurological image, or the responses made to the units firing, determine the conscious perception, not the image itself.

But the puzzle of the retinal image goes much deeper than this. There are other and even more radical discrepancies between the retinal images and perception. The attempted solutions get ever more elaborate (Wolfgang Köhler, Ivo Kohler, Von Holst, Held, Taylor, etc.). Moreover, it can be argued that the "retinal image" is not a screen-image at allñthat it is not even cognate with perception, and that the puzzle of rearranging or correcting, or compensating, or interpreting, or processing the messages of retinal points is insoluble.

Ecological optics provides a new starting point for a physiology of perception based not on form-sensations (or perceptions) from the retina but on information pickup from the ambient light. If one considers the form sensations coming from the two lateral eyes of a fish, each specifying half of the environment, it becomes evident that these sensations cannot be the basis for the perceptual ability of the fish.