ENCODING AND JUDGMENT OF SENSORY MAGNITUDES

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The overall objective is to understand how sensory stimuli are encoded, perceived, and judged. The main determinants of such basic sensory properties as loudness and pitch in hearing, brightness and color in vision, the strength of warm and cold sensation, are the make-up and intensity of the current physical stimulus. Nevertheless, perceptual judgments also depend in important ways on the possible stimuli that may occur or that have occurred in the past; that is, perceptual judgments are contextual. A basic measure within sensory science -- sensory matches between qualitatively different stimuli -- can depend significantly on stimulus context. The present research uses a new experimental paradigm, called dynamic psychophysical scaling, to evaluate the encoding and judgment of various dimensions of sensory experience -- intensity (e.g., loudness), quality (e.g., pitch), perceived duration, and perceived spatial extent -- in four sensory modalities (hearing, vision, touch, temperature). In dynamic scaling, subjects judge the magnitudes of sets of stimuli whose average values (e.g., of sound intensity, sound frequency) increase and decrease over time. In particular, when two qualitatively different stimuli are judged, each is judged relative to its own frame-of-reference, which depends on the contextual sets of stimulus intensities. When the context changes, the frames-of-reference can change slowly over time. The proposed research will attempt to develop a quantitative, parametric account of dynamic perceptual encoding and judgment. Previous research seems largely to have failed to incorporate both the short-term and long-term characteristics of these important perceptual processes, which are central to understanding basic properties of sensory functioning, including perception and judgment in cases of sensory deficit, loss, or disorder.