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Sensation and Perception All is not as it appears!!

Sensation and Perception All is not as it appears!!. Sensation The process by which our sense organs respond to and translate stimuli into nerve impulses sent to the brain. Perception Organizing the stimulus input and giving it meaning. Sensation and Perception. Sensation and Perception.

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Sensation and Perception All is not as it appears!!

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  1. Sensation and Perception All is not as it appears!!

  2. Sensation The process by which our sense organs respond to and translate stimuli into nerve impulses sent to the brain Perception Organizing the stimulus input and giving it meaning Sensation and Perception

  3. Sensation and Perception • Stages of sensation and perception • Stimuli activate sensory receptors • Sensory receptors translate information into nerve impulses • Specialized neurons analyze stimuli features • Stimulus pieces are reconstructed and compared to stimuli in memory • Perception is then consciously experienced

  4. Absolute limits of sensitivity Dimmest light in which we can see objects Softest sound we can hear Recognizing differences between stimuli Smallest difference in brightness detectable Recognizing differences between tones Psychophysics: Studies of Sensitivity to Stimuli

  5. Stimulus Detection • The Absolute Threshold • The lowest intensity at which a stimulus can be detected 50% of the time

  6. Signal Detection Theory • Decision criterion: A personal standard of certainty before a person will say that they detect a stimulus • Affected by: • Conservativeness or boldness • Increasing rewards for hits or costs for misses

  7. Subliminal Perception • A subliminal stimulus cannot be perceived consciously but do register in the nervous system • “subliminal perception”

  8. Subliminal Perception: Research Results • Stimuli above threshold influence behavior much more than subliminal stimuli • Subliminal stimuli have stronger effects on attitudes • Effects may be due to placebo effects

  9. The Difference Threshold • The difference threshold (just noticeable difference or JND) is the smallest difference between two stimuli that people can perceive 50% of the time • Weber’s Law: the JND is directly proportional to the magnitude of the stimulus with which the comparison is made (e.g 1/50 for weight)

  10. Sensory Adaptation (Habituation) • Sensory neurons respond to a constant stimulus by decreasing their activity

  11. The Sensory Systems: Vision • Lens: • Becomes thinner to focus on distant objects and thicker to focus on closer ones • Rods: Black and white receptors • Cones: Color receptors

  12. The Sensory Systems: Vision • Transduction • Absorption of light by photopigments produces a chemical reaction changing the rate of neurotransmitter release at the receptor’s synapse • The greater the change in release, the stronger the signal passed into the optic nerve

  13. The Sensory Systems: Vision • Dark Adaptation • Photopigment molecules are regenerated, increasing receptor sensitivity • Cones reach maximum sensitivity in 5 minutes; rods take 1/2 hour

  14. Young-Helmholtz trichromatic theory Individual cones are most sensitive to wavelengths corresponding to: Blue Green Red Opponent Process Theory (Hering, 1870) Three cone types respond to two different wavelengths Red/Green Blue/Yellow Black/White The Sensory Systems: Vision

  15. The Sensory Systems: Vision • Dual-Process Theory • Trichromatic theory confirmed • Opponent processes occur in the ganglion cells of the retina rather than the cones

  16. Dichromat Blind in Red - Green or Yellow - Blue systems or both Monochromat Sensitive only to the Black - White system The Sensory Systems:Color Blindness

  17. The Sensory Systems: Audition • Characteristics of sound waves • Frequency: the number of sound waves, or cycles, per second (measured in Hz) • Amplitude: the vertical size of the sound waves (measured in dB)

  18. The Sensory Systems: Auditory Transduction 1. Sound waves strike eardrum, setting cochlear fluid into motion 2. Fluid waves vibrate the basilar membrane, bending the hair cells in the organ of Corti 3. Neurotransmitters are released into the synapse, resulting in a nerve impulse

  19. Frequency Theory Nerve impulses sent to the brain match the frequency of the sound wave Place Theory There is a specific point in the cochlea where the fluid wave peaks and most strongly bends the hair cells Audition: Theories of Pitch

  20. The Sensory Systems: Audition • Sound localization • Sounds arrive first at the ear closest to the sound • Judgments of sound intensity also affect localization

  21. The Sensory Systems: Audition • Types of Deafness • Conduction • Caused by problems transmitting sound waves to cochlea • Nerve deafness • Caused by damaged receptors in inner ear or damaged auditory nerve

  22. The Sensory Systems: Gustation • A “taste” results from complex patterns of neural activity produced by the four types of taste receptors

  23. The Sensory Systems: Olfaction • Humans have about 40 million olfactory receptors.

  24. The Sensory Systems: Olfaction • Menstrual Synchrony • The tendency of women who live together or are close friends to become similar in their menstrual cycles • May be due to pheromones (Preti et al., 1986), but synchrony was not found in cohabiting lesbian couples (Weller & Weller, 1997, 1998)

  25. The Sensory Systems: The Tactile Sensations • Humans are sensitive to: • Pressure (touch) • Pain • Warmth • Cold

  26. The Sensory Systems: The Body Senses • Kinesthesis • Provides us with feedback about our muscles and joints’ positions and movements

  27. Bottom-up processing Taking individual elements of a stimulus and combining them into a perception Top-down processing Using existing knowledge in perception Attention: Focusing on certain stimuli Filtering out other information Perception: The Creation of Experience

  28. Stimulus factors in attention !!!Intensity!!! Novelty Movement Contrast Repetition Repetition Personal factors in attention Motives Interests Perception: The Creation of Experience

  29. Gestalt Principles of Perceptual Organization

  30. Gestalt Principles of Perceptual Organization

  31. Gestalt Principles of Perceptual Organization • Figure-Ground Relations

  32. Perception: The Creation of Experience • Perceptual schemata: allow us to classify sensory input in a top-down fashion • Perceptual set: A readiness to perceive stimuli in a particular way • Perceptual constancies: Allow us to recognize familiar stimuli under varying conditions

  33. Monocular cues Light and shadow Linear perspective Interposition Height in the horizontal plane Texture Clarity Relative size Motion parallax Binocular cues Binocular disparity Convergence Depth Perception

  34. Perception: The Creation of Experience • Illusions are false perceptions

  35. Understanding Pain • Endorphins: Natural opiates inhibit the release of neurotransmitters involved in pain perception • Stress-induced analgesia: A reduction in perceived pain that occurs under stressful conditions • Adaptive for functioning so that a person can deal with the stressful stimulus

  36. Psychology and Pain Can psychology help people suffering from pain? http://www.crha-health.ab.ca/clin/adultpsy/features/chronic.htm

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