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Understanding Sensation and Perception: Mechanisms and Variations Across Species

This article explores the intricate processes of sensation and perception, detailing how stimuli stimulate receptors and how the brain interprets these sensations. It discusses variations in sensory capabilities among species and individuals, information processing methods (bottom-up and top-down), and the role of stimuli quality and quantity. The concepts of sensory adaptation, perceptual processes, depth perception, and disorders in perception, including illusions and hallucinations, are examined, providing a comprehensive overview of how we perceive our complex world.

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Understanding Sensation and Perception: Mechanisms and Variations Across Species

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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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