TEMPORAL ASYMMETRY AND “MAGNET EFFECT” IN SIMILARITY AND DISCRIMINATION OF PROTOTYPICAL AND NONPROTOTYPICAL STIMULI: CONSEQUENCES OF DIFFERENTIAL SENSATION WEIGHTING

  • Ã…ke Hellström

Abstract

The judged similarity between two successive stimuli is higher when the less prototypical sti- mulus is the first in the pair than when it is the last. Also, the rated similarity between a scalar and a nonscalar melody is greater when the nonscalar melody comes first rather than last in the pair, and a change from a mistuned to a tuned musical interval is harder to detect than when the order is reversed. Such time-order asymmetries can be accounted for by a generalization of Hellström’s sensation-weighting model, with a lower weight for the first stimulus as is usual when two successive stimuli are compared. This would result in assimi- lation of a first-presented nonprototypical stimulus toward the prototype, increasing its similarity to a more prototypical last-presented stimulus. Also, fewer “different†judgments, but not worse discrimination from variants, occur for prototypical than for nonprototypical stimuli; the so-called perceptual magnet effect appears to be a methodology-based artifact.

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