Swinging Door Invariants: Optical Information from Rotating Panels

Abstract Ecological perceptual research focuses on stimulus array invariants as information that might guide organismic (particularly human) actions. Constructed by human agency, built environments entail structural regularities (e.g., planarity, verticality, horizontality, orthogonality) that constrain stimulus array information; here the emphasis is optical information (invariants). Built environments involve barriers that restrict behavior; doors allow passage through such barriers. Doors (more generally, swinging panels) yield surprisingly many instances of optical information. Specifically, invariants exist for (a) panel collision and bypass, (b) the panel’s axis of rotation, (c) the horizon line, and (d) the panel’s frontal-parallel orientation. Affordances are associated with each of those. Invariants described exemplify meta-invariant patterns (i.e., similarities in invariant stimulus array structure that occur across disparate environmental objects and events); meta-invariants may serve as research heuristics for the discovery of invariants in delimited contexts. Empirical considerations for optical invariants identified are described. Derivations described may be helpful for teaching the concept of invariants from stimulus array transformations, as well.