Résumé
The ecological notion of specification is traditionally understood within a single perceptual modality, with the structure of a given ambient (say optic) energy uniquely related to physical reality. The experiment evaluates the existence of the global array in the context of layout perception, which is often assumed to rely on vision. It formalized an intermodal invariant (i.e., a parameter of the global array) specifying the egocentric distance between a moving observer and astatic object. Three main conditions were tested: Vision-Movement (VM), Vision only (VO), Movement only (MO). Egocentric distance was specified only in the VM condition, and the researchers expected participants to detect it only in that condition. Reachability judgments were precise only when the relation between energy flows was preserved (VM condition). Judgement accuracy in that condition corresponded to the actual reaching distance, but was slightly overestimated (5%). Judgements in the VO and MO conditions were close to random.