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[Cognitive processes in perception: perceptive knowledge].

In an information processing approach, this paper attempt to show how different levels of processing visual information can be organized Sensory processing makes local coding of some dimensions. Then comme a step of structuration consisting in "putting together" these locally coded dimensions. These informations have finally to be interpreted on the basis of cognitive representations. Several examples are presented illustrating how ambiguities can appear between sensory information and various cognitive interpretations.

Cognition↗
PubMed2003

Heaviness perception. IV. Weight x aperture -1 as a heaviness model in finger-grasp perception.

The present study verified that a simple division of Weight/Aperture (W/A) from information obtained from the individual cubes could describe perceived heaviness when pairs of cubic objects were haptically held one-by-one for comparison utilizing a thumb/index finger grasp. To test the effect of W/A, 15 subjects judged the heaviness between a pair of cubes in three experimental conditions with all visual and material input blocked: (1) cubes with similar ratios, but different weights; (2) cubes with different ratios, but of the same weight; and (3) cubes with dissimilar ratios and weights. The largest percentage of errors (67.4%) was made when objects with similar ratios but different weights were presented, because subjects tended to perceive these objects as being of equal weight. In the condition "equal weight and different ratio", the percentage of correct responses (17.7%) was relatively small, as the subjects tended to perceive the objects as being of different weights. These results strongly suggest that the W/A ratio is an authoritative model to explain human performance in the process of discriminating heaviness. The division model is proposed as Weight x Aperture(-1) on the basis of a recently expounded concept of multiplicative neural circuits.

Adolescent↗
PubMed2002

Are mechanisms for perception of biological motion different from mechanisms for perception of nonbiological motion?

We compared the integration of information over space and time for perceiving different configurations of moving dots: a walking person (biological motion), rigid three-dimensional shapes, and unidirectional coherent motion of all dots (translation). No performance differences in judging walking direction and coherent translation direction were obtained in conditions with constant presentation times and varying number of target dots (integration over space). Depending on the speed of the two-dimensional configurations judgments were either worse or better than the judgments of walking direction. The results for conditions with different presentation times (integration over time) show that information about biological motion is integrated over time that increases with increasing gait period, while two-dimensional unidirectional motion is integrated over constant time independent of speed. The effect is not due to the oscillatory nature of the biological motion since information about a rigid three-dimensional shape is summed over a constant time independent of the period of the motion cycle. This could be interpreted as different neural mechanisms mediating the temporal summation for walking direction compared to detecting the orientation of rigid structure, or the direction of two-dimensional unidirectional motion. Since biological motion is characterized by nonrigidity, it is possible that the form itself is integrated over time and not the motion pattern.

Algorithms↗