Monocular Movement Parallax and Near-Space Perception

Abstract

Monocular perception of absolute distances in near space (<2 m) is discussed and studied experimentally. Stimulus change in time and sensory co-action (visual plus kinestethic) are in the theoretical analysis regarded as essential. Therefore movement parallax due to voluntary head movements has been introduced, in the experiments, as a hypothetical main cue, and perspective pattern transformation as a probably important side cue together with accommodation. (In ‘natural’ monocular perception these cues, in combination, are always available in near-space perception.) Under these experimental conditions all subjects exhibited approximately adequate (veridical) distance perception. This positive result, which diverges from the commonly accepted views about absolute-distance information, is tentatively regarded as an effect of the combination of cues and of methodological improvements introduced in the experiments. The result is taken as an indication of the fruitfulness of Gibson's conception of perceptual systems.