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CHAPTER 4

CHAPTER 4. Sensation & Perception. Lecture Overview. Introduction to Sensation & Perception Understanding Sensation How We See and Hear Our Other Senses Understanding Perception. Sensation and Perception. Sensation

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CHAPTER 4

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  1. CHAPTER 4 Sensation & Perception

  2. Lecture Overview • Introduction to Sensation & Perception • Understanding Sensation • How We See and Hear • Our Other Senses • Understanding Perception

  3. Sensation and Perception • Sensation • process of receiving, converting, and transmitting raw sensory information from the external and internal environments to the brain • Perception  • process of selecting, organizing, and interpreting sensory information

  4. Sensation Versus Perception When you stare at the cube on the left, which area is the top, bottom, or back? In the figure on the right, is this a young woman looking to the right, or an older woman with her chin buried in her jacket?

  5. Sensation Vs. Perception

  6. SENSATION

  7. Processing • Processing • sensory organs contain receptors that receive sensory information from the environment

  8. Processing • Three Types of Processing: • Transduction: • Converts sensory stimuli into neural impulses • Sensory reduction: • Filters/analyzes incoming sensations before sending to the brain • Coding: • Converts sensory input into a specific sensation sent to the brain

  9. Processing All processing occurs at the sensory level and messages are then sent on to the brain.

  10. Thresholds • Psychophysics: Testing limits and changes • Absolute Threshold: • smallest amount of a stimulus we can detect • Difference Threshold: • Min. difference needed to detect a stimulus change; also called the just noticeable difference (JND)

  11. Sensory Thresholds Vision A candle flame seen at 30 mi. on a clear, dark night The tick of a watch under quiet conditions at 20 ft. Hearing Taste One teaspoon of sugar in 2 gallons of water Smell 1 drop of perfume diffused into the entire volume of a 3 room apartment The wing of a bee falling on your cheek from a height of 1 cm Touch

  12. Sensory Thresholds • Weber’s Law • to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount) • light intensity - 8% • Weight - 2% • tone frequency - 0.3%

  13. Thresholds • Sensory Adaptation: • decreased sensory response to continuous stimulation

  14. How We See: Vision • Light is a form of electromagnetic energy that moves in waves • Many types of electromagnetic waves form the electromagnetic spectrum

  15. Electromagnetic Spectrum

  16. Electromagnetic Spectrum The flower on the left looks normal to us, whereas the one on the right was photographed under ultraviolet light

  17. How We See: Light Waves • Light waves vary in: • length (wavelength), which determines frequency (hue or color) • height (amplitude), which determines brightness or intensity

  18. Anatomy of the Eye • The function of the eye is to capture light waves and focus them on receptors at the back of the eyeball.

  19. Structures of the Retina • Receptors for vision are the rods and cones located in the retina.

  20. Are You Nearsighted or Farsighted? • Myopia: • Near sightedness • Focused in front of retina • Hyperopia: • Far sightedness • Focused behind retina

  21. Optic Nerve, Blind Spot & Fovea Optic nerve: Carries neural impulses from the eye to the brain Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. Fovea: Central point in the retina around which the eye’s cones cluster.

  22. Photoreceptors E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969

  23. Visual Information Processing Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex.

  24. Feature Detection • Feature Detection: • Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement.

  25. Shape Detection Specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs and houses.

  26. How We Hear:Audition • Sound results from movement of air molecules in a particular wave pattern. • Sound waves vary in: • Length which determines pitch (highness or lowness). • Height which determines loudness

  27. How We Hear:Audition • The loudness of a sound is measured in decibels. Constant noise above 90 decibels can cause permanent nerve damage to the ear.

  28. How We Hear: Anatomy of the Ear Receptors for hearing are hair cells located in the cochlea.

  29. Our Other Senses • Our sense of smell is called olfaction. • Receptors for smell are embedded in a nasal membrane, the olfactory epithelium.

  30. Gustation (Sense of Taste) • Receptors for gustation are taste buds, located in the papillae on the surface of the tongue.

  31. Three Body Senses • Skin sensesinvolvethree basic skin sensations • Touch (or pressure) • Temperature • Pain • Receptors for these sensations occur in various concentrations and depths in the skin.

  32. Three Body Senses Vestibular sense (or sense of balance) involves the vestibular sacsand semicircular canals located in the inner ear.

  33. Three Body Senses • Kinesthesia provides the brain with information about bodily posture and bodily movement • Kinesthetic receptors are found throughout the muscles, joints, and tendons of the body.

  34. UNDERSTANDING PERCEPTION Chapter 4

  35. Understanding Perception • Illusions: • false or misleading perceptions help scientists study the processes of perception (e.g., the horizontal-vertical illusion)

  36. The Muller-Lyer Illusion Which vertical line is longer?

  37. Understanding Perception Do You See the Cow?

  38. Understanding Perception Now Can You See the Cow?

  39. Understanding Perception • Perception’s three basic processes: • Selection • Organization • Interpretation

  40. Selection • Selection(choosing where to direct attention) involves these factors: • Selective Attention • filtering out and attending only to important sensory messages (cocktail party conversations) • Habituation • brain’s tendency to ignore environmental factors that remain constant

  41. Selection Kittens raised with only vertical visual stimuli fail to develop the ability to detect horizontal lines. Can you explain why?

  42. Organization • Organization: assemblingof information into patterns that help us understand the world • We organize sensory information in terms of: • Form • Consistency • Depth • Color

  43. Form Perception • Gestalt psychologists developed laws explaining how people perceive form according to: • Figure and ground • Ground is always seen as farther away than the figure • Proximity • Objects that are physically close together are grouped together

  44. Form Perception • Gestalt laws cont’d • Continuity • Objects that continue a pattern are grouped together • Closure • The tendency to see a finished unit from an incomplete stimulus • Similarity • Similar objects are grouped together

  45. Grouping Principles The Gestalt Grouping Principles are in use here

  46. Form Perception Form Perception: Can You Explain These Impossible Figures?

  47. Organization • Perceptual Constancy: • Tendency to perceive the environment as remaining the same even with changes in sensory input. • Four best-known constancies: • Size • Shape • Color • Brightness

  48. Organization Can You Identify theSize, Shape, Color, and Brightness Constancies?

  49. The Ames Room Illusion

  50. Interpretation

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