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 References to these essays must cite them explicitly as unpublished manuscripts.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

The hypothesis that things have affordances, and that we perceive or learn to perceive them, is very promising, radical, but not yet elaborated (Perceptual Systems, p. 285). Roughly, the affordances of things are what they furnish, for good or ill, that is, what they afford the observer. A list of examples and a classification is needed; the reader is invited to make his own list, or to supplement the tentative list given below.
Not only objects but also substances, places, events, other animals, and artifacts have affordances. We might begin with the easy-to-perceive components of the environment consisting of surfaces and surface layouts. And we should assume a human animal as observer, to start with, since the list of affordances will be somewhat different for different animals.
I assume that affordances are not simply phenomenal qualities of subjective experience (tertiary qualities, dynamic and physiognomic properties, exc.). I also assume that they are not simply the physical properties of things as now conceived by physical science. Instead, they are ecological, in the sense that they are properties of the environment relative to an animal. These assumptions are novel, and need to be discussed.
In a theory of information - based perception, learning to perceive affordances is only one kind of perceptual learning or perceptual development. (For other kinds, see Perceptual Systems, Ch. 13, esp. p. 283 ff. and Principles, Ch. 5.)

The examples that follow are intended to be only suggestive.

I. Surfaces and surface-layouts related to posture and locomotion - a vertical rigid surface, an obstacle, affording collision and barring locomotion. - a sit-on-able surface (affording sitting).- a stand-on-able object, stool, affording a high reach.- a climbable layout (tree, ladder, stairway).

[list has been abridged]

VI. The detecting of affordances by young animals
The human young must learn to perceive these affordances, in some degree at least, but the young of some animals do not have time to learn the ones that are crucial for survival. Ethologists therefore are interested in what they call "sign-stimuli" and "releasers." If the foregoing is correct, however, the behavior in question should be reconsidered in terms of stimulus information, not of stimuli. A listing of releasers in these terms would be interesting.