The Analysis of Spatio-Temporal Organization
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 References to these essays must cite them explicitly as unpublished manuscripts.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.
Michotte was the first to demonstrate that, when we see one billiard ball cause another to move by impact, it is because the spatio-temporal organization in the light to the eye “directly unleashes this impression in us” (Oldfield, p. vii. in the introduction to Michotte, Perception of Causality, 1963). Slight changes in the spatial or temporal variables in the light destroy the impression. Michotte isolated the optical conditions for the perception of certain causal events and also, in the “tunnel effect”, the conditions for the perception of occlusion. But he did so by experimental ingenuity, not by a theoretical analysis of “spatio-temporal organization”. The term is vague and loose. How can we describe it precisely? What stimulus information exists in spatio-temporal organization? How can we talk about it intelligently?
The terms that seem to be promising for this analysis are as follows:
Optic Array. Also the structure of an optic array and the notion of subordinate and superordinate structure.
Optical Motion, or displacement. This is sharply distinguished from physical motion.
Optic Event, as distinguished from material event.
Optical Transformation, including perspective transformation.
Invariant under transformation.
The notions of adjacent order, and successive order, and permutation order (it does not seem to be possible to permute successive order).
The notions of continuity and discontinuity.
The notions of onset and cessation.
The notion of accretion to an optic array and deletion from an optic array as contrasted with persistence of an optic array. (Also progressive accretion or deletion, and possibly rate.)
With these terms, we can go on to describe environments and points of observation. We can now talk about the projection of environmental surfaces in an optic array and the occlusion of surfaces from an optic array. The optical transitions between projection and occlusion on the reverse can be specified. And the perception arising from concealing and revealing can be experimentally studied.