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Sensation and Perception

Sensation and Perception. 1 9 th October 200 7 tomesova @ ftvs.cuni.cz. Information-processing system. Sensation: stimulation of receptors - registered in the brain Perception: brain interprets sensations. Differences in sensory and perceptual capabilities.

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Sensation and Perception

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  1. Sensation and Perception 19th October 2007 tomesova@ftvs.cuni.cz

  2. Information-processing system • Sensation: stimulation of receptors - registered in the brain • Perception: brain interprets sensations

  3. Differences in sensory and perceptual capabilities • Among species (dog x men’s range of hearing) • Among individuals (taste preferences) • Why? • Variations in how sensory systems are structured • Higher order processes

  4. Processing information: • “bottom-up,” or data driven processing • “top-down,” or conceptually driven processing

  5. Stimulus • The quality of a stimulus (color, musical pitch) • The quantity of a stimulus (brightness, loudness)

  6. Stimulus detection • Sensory threshold • Distracting factors: • Background noise • Spontaneous activities of sensory cells • Motivation (costs) • Expectations

  7. Stimulus discrimination • Weber - Fechner’s law the amount by which a stimulus must be increased to produce a just noticeable difference tends to be a constant proportion of the initial stimulus intensity

  8. Sensory adaptation • Reduced ability to provide information after prolonged, constant stimulation • Why? • Sensitivity to CHANGES

  9. Perceiving a complex world • Direct perspective: all the information comes from the outer world • Constructivist perspective: we must supplement it with additional information stored in memory • schemas

  10. Expectations and perceptions • Perceptual set • Expectations based on schemas

  11. Basic perceptual processes • Form perception • Perceptual constancy • Depth perception

  12. Form perception • Gestalt psychologists (Max Wertheimer, Kurt Koffka, Wolfgang Kohler) • Subjective contours • Rules or principles of perceptual grouping • Overestimation of bottom-up processing

  13. Figure and groundBottom-up and top-down processing

  14. Depth perception • Binocular disparity • Monocular depth cues • Motion parallax • Relative size • Relative closeness to horizon • Linear perspective • Texture gradient • Partial overlap • Light and shadow

  15. Disorders of perception • Sensory distortions • changes in quality, intensity, spatial form of perception (toxic state, depression, migraine…) • Sensory deceptions • Illusions • Hallucinations

  16. Hallucinations • Perceptions which arise in the absence of any external stimulus (false perception) • unwilled - not subject to conscious manipulations • same qualities as a real perception • perceived as being located in the external world • auditory, visual, olfactory, gustatory • hypnogogic (visual or auditory) • palinopsia (reappearance - Parkinson’s) • of bodily sensations (temperature, touch, fluid)

  17. Illusions • involuntary false perception consequent on a real object in which a transformation of the object takes place • distortions of real objects • extreme tiredness and emotions • completion (banished by attention) • affective (fear) • pareidolic (shapes in clouds)

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