Chapter 3
Sensation and Perception




                  This multimedia product and its content are protected under
     ...
Chapter 3 Overview
   The process of sensation
   Vision
   Hearing
   Smell and taste
   The skin senses
   Balance...
The Process of Sensation

   Sensation is the process through
    which the senses pick up visual,
    auditory, and othe...
What is the difference between
the absolute threshold and the
difference threshold?
   What is the softest sound you can ...
Absolute threshold

   The minimum
    amount of sensory
    stimulation that can
    be detected 50% of
    the time



...
Difference threshold

   The smallest increase or decrease in a
    physical stimulus required to produce a
    differenc...
Weber’s Law

   The JND for all senses depends on a
    proportion or percentage of stimulus change
    rather than on a ...
How does transduction enable the
brain to receive sensory
information?
   Sensory receptors are highly specialized cells ...
Vision
   Our eyes respond to light in
    the visible spectrum
    – The band of electromagnetic
      waves visible to ...
How does each part of the eye
function in vision?
   Cornea
    – Tough, transparent
      protective layer that
      co...
How does each part of the eye
function in vision?
   Retina
    – Contains sensory receptors
      for vision
   Rods
  ...
What path does visual information
take from the retina to the primary
visual cortex?
   Optic nerve
    – Caries visual i...
How do we detect the difference
between one color and another?

   An apple’s skin looks red
    because it absorbs short...
What two major theories
attempt to explain color vision?
   Trichromatic Theory
    – Three types of cones in the retina ...
A negative afterimage




         Copyright © 2008 Allyn & Bacon
Hearing

   Sound requires a medium, such as air
    or water, through which to move
   First demonstrated by Robert Boy...
What determines the pitch and
loudness of sound, and how is each
quality measured?
   Frequency
    – The number of cycle...
Decibel levels of various sounds
Figure 3.5
The loudness of a sound (its
amplitude) is measured in
decibels. Each increase...
How do the outer ear, middle ear,
and inner ear function in hearing?

   Outer ear
    – Visible part of the ear,
      c...
What two major theories
attempt to explain hearing?
   Place theory
    – Each individual pitch is determined by the
    ...
Smell and Taste

   Olfaction
    – The sense of smell
   Gustation
    – The sense of taste




                   Copy...
What path does a smell message
    take from the nose to the brain?

   Olfactory epithelium
     – Two 1-inch square pat...
What are the primary taste
sensations, and how are they
detected?
   Traditionally, four primary taste sensations
    hav...
What are the primary taste
sensations, and how are they
detected?




    Taste sensations are detected by receptor cells...
The Skin Senses

   Include the senses of touch and pain
   These senses are critical for survival




                 ...
How does the skin provide
sensory information?
   When an object touches and depresses the
    skin it stimulates recepto...
What is the function of pain, and how is
pain influenced by psychological factors,
culture, and endorphins?
   Pain serve...
Balance and Movement

   The kinesthetic and vestibular
    senses provide information about
    where the parts of the b...
What kinds of information do the
kinesthetic and vestibular senses
provide?
   The kinesthetic sense provides
    informa...
What kinds of information do the
kinesthetic and vestibular senses
provide?




   The vestibular sense detects movement ...
Influences on Perception

   Perception is the process through
    which the brain assigns meaning to
    sensations
   ...
What is gained and what is lost
in the process of attention?
   Attention is the process of sorting through
    sensation...
How does prior knowledge
influence perception?
   Bottom-up processing
    – Information processing in which individual b...
How does information from
multiple sources aid perception?

   Cross modal perception
    – The process by which the brai...
Principles of Perception

   A few principles govern perceptions in
    all humans




                  Copyright © 2008...
What are the principles that govern
perceptual organization?




   Gestalt principles of perceptual organization
     – ...
What are some of the binocular
and monocular depth cues?
   Depth perception
    – The ability to perceive the visual wor...
Binocular disparity
   Enables most of us to see 3-D images in stereograms




                          Copyright © 2008...
Monocular depth cues




          Copyright © 2008 Allyn & Bacon
How does the brain perceive
motion?
   The brain perceives real motion by
    comparing the movement of images
    across...
What are three types of
puzzling perceptions?




    Ambiguous figures
     – The perceptual system tries to resolve the...
What are three types of
puzzling perceptions?




   Illusions
     – False perceptions or misperceptions of an actual st...
Unusual Perceptual
Experiences
   Subliminal perception
    – The capacity to perceive and respond to
      stimuli that ...
In what ways does subliminal
perception influence behavior?
   Research suggests that subliminal
    information can infl...
What have studies of ESP
shown?
   Some studies have suggested that ESP
    exists
   But, in almost all cases, attempts...
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Chapter 3

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Chapter 3

  1. 1. Chapter 3 Sensation and Perception This multimedia product and its content are protected under copyright law. The following are prohibited by law: Any public performance or display, including transmission of any image over a network. Preparation of any derivative work, including the extraction, in whole or in part, of any images. Any rental, lease or lending of the program. Copyright © 2008 Allyn & Bacon
  2. 2. Chapter 3 Overview  The process of sensation  Vision  Hearing  Smell and taste  The skin senses  Balance and movement  Influences on perception  Principles of perception  Unusual perceptual experiences Copyright © 2008 Allyn & Bacon
  3. 3. The Process of Sensation  Sensation is the process through which the senses pick up visual, auditory, and other sensory stimuli and transmit them to the brain  Perception is the process by which the brain actively organizes and interprets sensory information Copyright © 2008 Allyn & Bacon
  4. 4. What is the difference between the absolute threshold and the difference threshold?  What is the softest sound you can hear and the dimmest light you can see?  How much must the volume be turned up or down for you to notice a difference in the loudness of music?  Researchers in sensory psychology have performed many experiments to answer these kinds of questions Copyright © 2008 Allyn & Bacon
  5. 5. Absolute threshold  The minimum amount of sensory stimulation that can be detected 50% of the time Copyright © 2008 Allyn & Bacon
  6. 6. Difference threshold  The smallest increase or decrease in a physical stimulus required to produce a difference in sensation that is noticeable 50% of the time  Just noticeable difference (JND) is the smallest change in sensation that a person is able to detect 50% of the time Copyright © 2008 Allyn & Bacon
  7. 7. Weber’s Law  The JND for all senses depends on a proportion or percentage of stimulus change rather than on a fixed amount of change – A 2% change is needed for a JND in a weight you are holding  a 1 lb difference is needed for a JND in a 50 lb weight  a 2 lb difference is needed for a JND in a 100 lb weight – Only a 0.33% change is needed for a JND in the pitch of a sound – Weber’s law best applies to people with average sensitivities and to stimuli that are not too strong or weak Copyright © 2008 Allyn & Bacon
  8. 8. How does transduction enable the brain to receive sensory information?  Sensory receptors are highly specialized cells in the sense organs that detect and respond to one type of sensory stimuli and transduce (convert) the stimuli into neural impulses  Transduction is the process through which sensory receptors convert sensory stimulation into neural impulses  Sensory adaptation is the process in which sensory receptors grow accustomed to constant, unchanging levels of stimuli over time – e.g., Smokers grow accustomed to smell of cigarettes Copyright © 2008 Allyn & Bacon
  9. 9. Vision  Our eyes respond to light in the visible spectrum – The band of electromagnetic waves visible to the human eye  Electromagnetic waves are measured in wavelengths – The distance from the peak of a light wave to the peak of the next wave Copyright © 2008 Allyn & Bacon
  10. 10. How does each part of the eye function in vision?  Cornea – Tough, transparent protective layer that covers front of eye – Bends light rays inward through the pupil  Lens – Transparent disk- shaped structure behind the iris and pupil – Changes shape as it focuses on objects at varying distances  This process is called Accommodation Copyright © 2008 Allyn & Bacon
  11. 11. How does each part of the eye function in vision?  Retina – Contains sensory receptors for vision  Rods – Receptor cells that allow eye to respond to low levels of light  Cones – Receptor cells that enable us to see color and fine detail  Fovea – Area at center of retina that provides the clearest and sharpest vision  Blind spot – Point in each retina where there are no rods or cones Copyright © 2008 Allyn & Bacon
  12. 12. What path does visual information take from the retina to the primary visual cortex?  Optic nerve – Caries visual information from each retina to both sides of the brain  Primary visual cortex – Part of the brain in which visual information is processed – Feature detectors respond to specific visual patterns, such as lines or angles Copyright © 2008 Allyn & Bacon
  13. 13. How do we detect the difference between one color and another?  An apple’s skin looks red because it absorbs short wavelengths and reflects long wavelengths  Hue – The specific color perceived  Saturation – The purity of a color  Brightness – The intensity of the light energy that is perceived as a color Copyright © 2008 Allyn & Bacon
  14. 14. What two major theories attempt to explain color vision?  Trichromatic Theory – Three types of cones in the retina each make a maximal response to one of three colors- blue, green, or red  Opponent-Process Theory – Three kinds of cells respond by increasing or decreasing their rate of firing when different colors are present  Red/green cells  Yellow/blue cells  White/black cells Copyright © 2008 Allyn & Bacon
  15. 15. A negative afterimage Copyright © 2008 Allyn & Bacon
  16. 16. Hearing  Sound requires a medium, such as air or water, through which to move  First demonstrated by Robert Boyle in 1660 – Watch in a jar experiment Copyright © 2008 Allyn & Bacon
  17. 17. What determines the pitch and loudness of sound, and how is each quality measured?  Frequency – The number of cycles completed by a sound wave in one second – Determines the pitch of a sound – Frequency is measured in hertz (Hz)  Amplitude – The loudness of sound – Amplitude is measured in decibels (dB)  Timbre – The distinctive quality of a sound that distinguishes it from other sounds of the same pitch and loudness – Example: A piano and guitar sound different when playing the same note Copyright © 2008 Allyn & Bacon
  18. 18. Decibel levels of various sounds Figure 3.5 The loudness of a sound (its amplitude) is measured in decibels. Each increase of 10 decibels makes a sound 10 times louder. A normal conversation at 3 feet measures about 60 decibels, which is 10,000 times louder than a soft whisper of 20 decibels. Any exposure to sounds of 130 decibels or higher puts a person at immediate risk for hearing damage, but levels as low as 90 decibels can cause hearing loss if one is exposed to them over long periods of time. Copyright © 2008 Allyn & Bacon
  19. 19. How do the outer ear, middle ear, and inner ear function in hearing?  Outer ear – Visible part of the ear, consisting of the pinna and auditory canal  Middle ear – Contains the ossicles, which connect the ear drum to the oval window and amplify sound waves  Inner ear – Cochlea: Fluid filled chamber that contains the basilar membrane and hair cells – Hair cells: Sensory receptors for hearing Copyright © 2008 Allyn & Bacon
  20. 20. What two major theories attempt to explain hearing?  Place theory – Each individual pitch is determined by the particular location along the basilar membrane of the cochlea that vibrates the most – Provides a good explanation of how we hear sounds with frequencies higher than 1000 Hz  Frequency theory – Hair cell receptors vibrate the same number of times per second as the wave sounds that reach them – Provides a good explanation of how we hear low-frequency sounds Copyright © 2008 Allyn & Bacon
  21. 21. Smell and Taste  Olfaction – The sense of smell  Gustation – The sense of taste Copyright © 2008 Allyn & Bacon
  22. 22. What path does a smell message take from the nose to the brain?  Olfactory epithelium – Two 1-inch square patches of tissue, one at the top of each nasal cavity, which contain olfactory neurons  Olfactory bulbs – Two structures above the nasal cavity where smell sensations first register in the brain  Orbitofrontal cortex – Receives messages from olfactory bulbs via the thalamus Copyright © 2008 Allyn & Bacon
  23. 23. What are the primary taste sensations, and how are they detected?  Traditionally, four primary taste sensations have been recognized – Sweet – Sour – Salty – Bitter  Recent research suggests that there is a fifth taste sensation – Umami – This sensation is triggered by glutamate Copyright © 2008 Allyn & Bacon
  24. 24. What are the primary taste sensations, and how are they detected?  Taste sensations are detected by receptor cells in the taste buds  Specialized receptors are activated by each flavor (sweet, sour, etc.) – These receptors send separate messages to the brain Copyright © 2008 Allyn & Bacon
  25. 25. The Skin Senses  Include the senses of touch and pain  These senses are critical for survival Copyright © 2008 Allyn & Bacon
  26. 26. How does the skin provide sensory information?  When an object touches and depresses the skin it stimulates receptors in the skin  These receptors send messages through nerve connections to the spinal cord, through the brainstem and midbrain, and to the somatosensory cortex  Areas on the skin vary in sensitivity to touch, as measured by the two-point threshold – Areas with greater sensitivity are more densely packed with touch receptors Copyright © 2008 Allyn & Bacon
  27. 27. What is the function of pain, and how is pain influenced by psychological factors, culture, and endorphins?  Pain serves as an early warning system for many potentially deadly situations  Pain can be influenced by several psychological factors – Focusing attention elsewhere reduces pain – Placebo effect reduces pain – Negative thoughts increase pain – Some cultures encourage individuals to suppress, or exaggerate, emotional reaction to pain  Endorphins are the body’s natural painkillers – They block pain and produce a sense of well-being Copyright © 2008 Allyn & Bacon
  28. 28. Balance and Movement  The kinesthetic and vestibular senses provide information about where the parts of the body are and where the body is located relative to the physical environment Copyright © 2008 Allyn & Bacon
  29. 29. What kinds of information do the kinesthetic and vestibular senses provide?  The kinesthetic sense provides information about the position of body parts in relation to each other and the movement of the entire body or its parts  This information is detected by receptors in the joints, ligaments, and muscles Copyright © 2008 Allyn & Bacon
  30. 30. What kinds of information do the kinesthetic and vestibular senses provide?  The vestibular sense detects movement and the body’s orientation in space  The vestibular sense organs are located in the semicircular canals and vestibular sacs in the inner ear – These organs sense rotation of the head Copyright © 2008 Allyn & Bacon
  31. 31. Influences on Perception  Perception is the process through which the brain assigns meaning to sensations  Perception is influenced by a number of factors, including – Attention – Prior knowledge – Cross-modal perception Copyright © 2008 Allyn & Bacon
  32. 32. What is gained and what is lost in the process of attention?  Attention is the process of sorting through sensations and selecting some of them for further processing  When attention is focused on some sensations, others are missed altogether or misperceived – Inattentional blindness occurs when attention is shifted from one object to another and we fail to notice changes in objects not receiving direct attention – The cocktail party phenomenon shows that we focus attention on information that is personally meaningful Copyright © 2008 Allyn & Bacon
  33. 33. How does prior knowledge influence perception?  Bottom-up processing – Information processing in which individual bits of data are combined until a complete perception is formed  Top-down processing – Information processing in which previous experience and knowledge are applied to recognize the whole of a perception – Perceptual set is an expectation of what will be perceived that can affect what is perceived Copyright © 2008 Allyn & Bacon
  34. 34. How does information from multiple sources aid perception?  Cross modal perception – The process by which the brain integrates information from more than one sense – Cross modal perception is used to process complex stimuli such as speech Copyright © 2008 Allyn & Bacon
  35. 35. Principles of Perception  A few principles govern perceptions in all humans Copyright © 2008 Allyn & Bacon
  36. 36. What are the principles that govern perceptual organization?  Gestalt principles of perceptual organization – Similarity: Objects that have similar characteristics are perceived as a unit – Proximity: Objects that are close together are perceived as belonging together – Continuity: Figures or objects are perceived as belonging together if they appear to form a continuous pattern – Closure: Figures with gaps in them are perceived as complete F Copyright © 2008 Allyn & Bacon
  37. 37. What are some of the binocular and monocular depth cues?  Depth perception – The ability to perceive the visual world in three dimensions and to judge distances accurately  Binocular depth cues depend on both eyes working together – Convergence – Binocular disparity  Monocular depth cues can be perceived by one eye alone Copyright © 2008 Allyn & Bacon
  38. 38. Binocular disparity  Enables most of us to see 3-D images in stereograms Copyright © 2008 Allyn & Bacon
  39. 39. Monocular depth cues Copyright © 2008 Allyn & Bacon
  40. 40. How does the brain perceive motion?  The brain perceives real motion by comparing the movement of images across the retina to reference points that it assumes to be stable  Autokinetic illusion – An unmoving light in a dark room appears to move  Your eyes are moving, not the light  In the dark, the brain has no stable reference point to determine what is moving Copyright © 2008 Allyn & Bacon
  41. 41. What are three types of puzzling perceptions?  Ambiguous figures – The perceptual system tries to resolve the uncertainty by seeing the figure first one way and then another  Impossible figures – May not seem unusual until you examine them closely and see the impossibility Copyright © 2008 Allyn & Bacon
  42. 42. What are three types of puzzling perceptions?  Illusions – False perceptions or misperceptions of an actual stimulus in the environment  Figure c shows the Müller-Lyer illusion  Figure d shows the Ponzo illusion Copyright © 2008 Allyn & Bacon
  43. 43. Unusual Perceptual Experiences  Subliminal perception – The capacity to perceive and respond to stimuli that are presented below the threshold of awareness  Extrasensory perception (ESP) – Gaining information about objects, events, or another person’s thoughts through means other than known sensory channels Copyright © 2008 Allyn & Bacon
  44. 44. In what ways does subliminal perception influence behavior?  Research suggests that subliminal information can influence behavior to some degree – But it appears to be ineffective at persuading people to buy products or vote in certain ways Copyright © 2008 Allyn & Bacon
  45. 45. What have studies of ESP shown?  Some studies have suggested that ESP exists  But, in almost all cases, attempts to replicate these studies have failed – So most psychologists remain skeptical about existence of ESP Copyright © 2008 Allyn & Bacon

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