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MOTION PERCEPTION DURING SELF-MOTION The Direct versus Inferential controversy revisited

Wertheim , Alexander H. (1994) MOTION PERCEPTION DURING SELF-MOTION The Direct versus Inferential controversy revisited.

Short Abstract:

According to the traditional inferential theory of perception, percepts of object motion or stationarity stem from an evaluation of afferent retinal signals (which encode image motion) with the help of extraretinal signals (which encode eye movements). Direct perception theory, on the other hand, assumes that the percepts derive from retinally conveyed information only. Neither view is compatible with a special perceptual phenomenon which occurs during visually induced sensations of ego-motion (vection). A modified version of inferential theory yields a model in which the concept of an extraretinal signal is replaced by that of a reference signal. Reference signals do not encode how the eyes move in their orbits, but how they move in space. Hence reference signals are produced not only during eye movements but also during ego-motion, (i.e., in response to vestibular stimulation and to retinal image flow, which may induce vection). The present theory describes how self-motion and object motion percepts interface. Empirical tests (using an experimental paradigm that allows quantitative measurement of the magnitude and gain of reference signals and the size of the Just Noticeable Difference (JND) between retinal and reference signals) reveal that the distinction between direct and inferential theories largely depends on: (1) a mistaken belief that perceptual veridicality is evidence that extraretinal information is not involved, and (2) a failure to distinguish between (the perception of) absolute object motion in space and relative motion of objects with respect to each other. The new model corrects these errors, thus providing a new, unified framework for interpretating many phenomena in the field of motion perception.

Long Abstract:

According to the traditional inferential theory of perception, percepts of object motion or stationarity stem from an evaluation of afferent retinal signals (which encode image motion) with the help of extraretinal signals (which encode eye movements). Direct perception theory, on the other hand, assumes that the percepts derive from retinally conveyed information only. Neither view is compatible with a special perceptual phenomenon which occurs during visually induced sensations of ego-motion (vection). A modified version of inferential theory yields a model in which the concept of an extraretinal signal is replaced by that of a reference signal. Reference signals do not encode how the eyes move in their orbits, but how they move in space. Hence reference signals are produced not only during eye movements but also during ego-motion, (i.e., in response to vestibular stimulation and to retinal image flow, which may induce vection). The present theory describes how self-motion and object motion percepts interface. Empirical tests (using an experimental paradigm that allows quantitative measurement of the magnitude and gain of reference signals and the size of the Just Noticeable Difference (JND) between retinal and reference signals) reveal that the distinction between direct and inferential theories largely depends on: (1) a mistaken belief that perceptual veridicality is evidence that extraretinal information is not involved, and (2) a failure to distinguish between (the perception of) absolute object motion in space and relative motion of objects with respect to each other. The new model corrects these errors, thus providing a new, unified framework for interpretating many phenomena in the field of motion perception.

Keywords:	motion perception, velocity perception, self-motion, extraretinal signal, efference copy, direct perception, visual-vestibular interactions.
Subjects:	Biology: Theoretical Biology Psychology: Cognitive Psychology Neuroscience: Neuroanatomy Neuroscience: Neural Modelling Neuroscience: Neurology Psychology: Perceptual Cognitive Psychology
ID code:	bbs00000463
Deposited by:	Alex H Wertheim on 01 May 2001