Chapter 6: Sensation and Perception

  1. Sensing the World: Some Basic Principles
  2. Sensation: The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
  3. Perception: the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
  4. Bottom-up processing: sensory analysis that starts at the entry level (sensory receptors) and moves to the brain
  5. Top-down processing: guided by higher level mental processing, as we construct perceptions drawing on experience and expectation.
  6. Psychophysics: the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them.
  7. Thresholds:
  8. Absolute: the minimum simulation needed to detect a particular stimulus 50% of the time
  9. Vary with age
  10. Signal detection
  11. Signal detection theory: predicts how and when we will detect the presence of a faint stimulus (signal) amid background stimulation (noise)
  12. Says there is no single absolute threshold and that it depends on
  13. Experience
  14. Expectation
  15. Motivation
  16. Fatigue
  17. Subliminal stimulation
  18. Subliminal: below one’s absolute threshold for conscious awareness
  19. Priming: the activation, often unconscious, of certain associations, thus predisposing one’s perception, memory, and response.
  20. Sometime s we feel what we do not know and cannot describe
  21. But does this actually lead to lasting persuasion?
  22. Greenwald (1991,1992) experiment says no
  23. Difference Thresholds
  24. Difference threshold (or just noticeable difference JND): the minimum difference between two stimuli required for detection 50% of the time.
  25. Weber’s Law: to be perceived as different, two stimuli must differ by a constant minimum percentage.
  26. Light: 8%
  27. Weight: 2%
  28. Tones: .3%
  29. Sensory Adaptation: diminished sensitivity as a consequence of constant stimulation
  30. After constant exposure to a stimulus, our nerve cells fire less frequently.
  31. We perceive the world not exactly as it is, but as it is useful for us to perceive it.
  1. Vision
  2. The Stimulus Input: Light Energy
  3. Transduction: conversion of one form of energy to another; in sensation, the transforming of stimulus energies into neural impulses our brains can interpret.
  4. What strikes our eye is electromagnetic energy that our visual system perceives as color.
  5. Electromagnetic spectrum
  1. Wavelength (high/low frequency): the distance from one peak to the next
  2. Determines hue (color)
  3. Intensity (great/small amplitude): the high of the waves
  4. Determines brightness
  1. The Eye
  1. The Retina
  2. Receives an upside down image, it itself doesn’t “see” a whole image

  1. The thalamus receives and distributes visual information
  2. Where the optic nerve leaves the eye, there are no cells and this leaves a blind spot.
  3. Rods: detect black, white and gray (6 million)
  4. Peripheral vision
  5. Twilight vision
  6. Cones: detect fine detail and color (20 million)
  7. Daylight
  8. Well-lit conditions
  1. Visual Information Processing

  1. Feature detection
  2. Nerve cells in that brain respond to specific features of the stimulus, such as shape, angle, or movement.
  3. Supercell clusters, See image p.241
  4. Parallel Processing
  5. Computers do step-by-step serial processing
  6. Brain uses parallel processing, doing many things at once (Gestalt)
  7. We can prove this through studying brain injuries
  8. Combines things like color, motion, form, and depth into one perceptual experience
  9. Color Vision
  10. “A tomato’s color is our mental construction.”
  11. “Color, like all aspects of vision, resides not in the object but in the theatre of our brains.”
  12. We can differentiate 7 million different color variations
  13. Young-Helmholtz trichromatic (three-color) theory
  14. Theory that the retina contains three different color receptors
  15. Red
  16. Green
  17. Blue
  18. Opponent-process theory
  19. Theory that opposing retinal processes enable color vision
  20. Red-green
  21. Yellow-blue
  22. White-black
  1. Hearing
  2. The Stimulus Input: sound Waves
  3. The Ears
  4. Ears transform vibrating air into nerve impulses, which our brain decodes as sounds.
  5. Amplitude: strength, determines loudness
  6. Frequency: length, determines pitch
  7. Measured in decibels

  1. Hearing Loss and Deaf Culture
  1. Other Important Senses
  2. Touch
  3. Kinesthesis: your sense of the position and movement of your body parts
  4. Located in sensors in your joints, tendons, bones, ears, and skin
  5. Vestibular sense: monitors you head’s position and movement
  6. Pain
  7. Biological Influences
  8. Gate-control theory: spinal chord contain a neurological gate that blocks pain signals or allows them to pass on to the brain.
  9. Psychological Influences
  10. Distraction
  11. Expectations
  12. Socio-cultural Influences
  13. Presence of others
  14. Empathy for others’ pain
  15. Cultural expectations
  16. Taste
  17. Sweet, Salty, Sour, Bitter, Umami
  18. Taste is evolutionary
  19. Taste is chemical
  1. Smell

  1. Perceptual Organization
  2. Form Perception
  3. Figure and Ground: the organization of the visual field into objects (the figures) that stand out from their surroundings (ground).
  4. Grouping
  5. Proximity
  6. Similarity
  7. Continuity
  8. Connectedness
  9. Closure
  1. Depth Perception
  2. Visual cliff: research shows that even infants can perceive depth
  3. Binocular cues: depth cues, such as retinal disparity, that depend on the use of two eyes
  4. Retinal disparity: by comparing images from the retinas in the two eyes, the brain computes distance; the greater the disparity between the two images, the closer the object.
  5. Floating finger sausage!
  6. Monocular cues
  7. Depth cues, such as interposition and linear perspective, available to either eye alone.
  8. Relative height
  9. Relative size
  10. Interposition
  11. Linear perspective
  12. Light and shadow
  13. Relative motion
  14. Motion Perception
  15. Perceptual Constancy
  16. Shape and Size
  17. Perceived size and perceived distance
  18. Lightness/ Brightness
  19. Relative luminance: the amount of light an object reflects relative to its surroundings
  20. Color
  21. Our experience of color comes not just from the object itself, but from everything around it as well.
  22. Perceptual Interpretation
  23. Sensory deprivation and restored vision
  24. Is perception due to nature or nurture?
  25. “Experience guides, sustains, and maintains the brain’s neural organization.”
  26. Sensory deprivation at young ages is particularly harmful
  27. “Critical period”
  28. Nurture sculpts what nature has endowed
  29. Perceptual Adaptation
  30. In vision, the ability to adjust to an artificially displaced to even distorted field
  31. George Stratton and the inverted world
  32. Perceptual Set
  33. A mental predisposition to perceive one thing and not another
  34. Schemas: concepts, organize and interpreter unfamiliar information
  35. If told there is vinegar in your beer, you will perceive it as tasting worse than if you are not told that (expectation) and most people report McDonald’s fries as better tasting when in a McDonalds bag than in a plain white one (I might be the opposite…as I generally hate McDonald’s fries…)
  36. Context effects
  37. Stereotypes
  38. Gender
  39. Race
  40. Differences exist in the perceptions of the beholder
  41. Emotion and Motivation
  42. Our emotions influence our perceptions
  43. It is bio-psycho-social
  44. Perception and the Human Factor
  45. Human factors: a branch of psychology that explores how people and machines interact and how machines and physical environments can be made safe and easy to use
  1. Is There Extrasensory Perception?
  2. ESP: controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition.
  3. Parapsychology: the study of paranormal phenomenon, including ESP
  4. 96% of scientists in the U.S. National Academy of Sciences are skeptical that such phenomena exist.
  5. Claims of ESP
  6. Telepathy: mind to mind communication
  7. Clairvoyance: perceiving remote events
  8. Precognition: perceiving future events
  9. Premonitions of Pretensions?
  10. Generating more predictions increases the odds of one of them being right
  11. Vague predictions are easier to interpret multiple ways
  12. The power of coincidence
  13. Putting ESP to the Experimental Test
  14. What parapsychology needs is a reproducible phenomenon and a theory to explain it.