Chapter 3Sensation and Perception                           1
Chapter 3 Overview   The process of sensation   Hearing   Smell and taste   The skin senses   Influences on perceptio...
The Process of Sensation   Sensation is the process through    which the senses pick up visual,    auditory, and other se...
What is the difference betweenthe absolute threshold and thedifference threshold?   What is the softest sound you can hea...
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    difference in...
How does transduction enable thebrain to receive sensoryinformation?   Sensory receptors are highly specialized cells in ...
Hearing   Sound requires a medium, such as air    or water, through which to move   First demonstrated by Robert Boyle i...
What determines the pitch andloudness of sound, and how is eachquality measured?   Frequency    – The number of cycles co...
Decibel levels of various soundsFigure 3.5The loudness of a sound (itsamplitude) is measured indecibels. Each increase of ...
What are the primary tastesensations, and how are theydetected?   Traditionally, four primary taste sensations    have be...
What are the primary tastesensations, and how are theydetected?    Taste sensations are detected by receptor cells in the...
The Skin Senses   Include the senses of touch and pain   These senses are critical for survival                         ...
How does the skin providesensory information?   When an object touches and depresses the    skin it stimulates receptors ...
What is the function of pain, and how ispain influenced by psychological factors,culture, and endorphins?   Pain serves a...
Influences on Perception   Perception is the process through    which the brain assigns meaning to    sensations   Perce...
What is gained and what is lostin the process of attention?   Attention is the process of sorting through    sensations a...
How does prior knowledgeinfluence perception?   Bottom-up processing    – Information processing in which individual bits...
Principles of Perception   A few principles govern perceptions in    all humans                                          ...
What are the principles that governperceptual organization?   Gestalt principles of perceptual organization     – Similar...
How does the brain perceivemotion?   The brain perceives real motion by    comparing the movement of images    across the...
What are three types ofpuzzling perceptions?    Ambiguous figures     – The perceptual system tries to resolve the uncert...
What are three types ofpuzzling perceptions?   Illusions    – False perceptions or misperceptions of an actual stimulus  ...
Unusual PerceptualExperiences   Subliminal perception    – The capacity to perceive and respond to      stimuli that are ...
In what ways does subliminalperception influence behavior?   Research suggests that subliminal    information can influen...
What have studies of ESPshown?   Some studies have suggested that ESP    exists   But, in almost all cases, attempts to ...
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Ch. 3 sensation and perception.key

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  • Ch. 3 sensation and perception.key

    1. 1. Chapter 3Sensation and Perception 1
    2. 2. Chapter 3 Overview The process of sensation Hearing Smell and taste The skin senses Influences on perception Principles of perception Unusual perceptual experiences 2
    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 3
    4. 4. What is the difference betweenthe absolute threshold and thedifference 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 4
    5. 5. Absolute threshold The minimum amount of sensory stimulation that can be detected 50% of the time 5
    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 6
    7. 7. How does transduction enable thebrain to receive sensoryinformation? 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 7
    8. 8. 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 8
    9. 9. What determines the pitch andloudness of sound, and how is eachquality 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 9
    10. 10. Decibel levels of various soundsFigure 3.5The loudness of a sound (itsamplitude) is measured indecibels. Each increase of 10decibels makes a sound 10times louder. A normalconversation at 3 feetmeasuresabout 60 decibels, which is10,000 times louder than a softwhisper of 20 decibels. Anyexposure to sounds of 130decibels or higher puts aperson at immediate risk forhearing damage, but levels aslow as 90 decibels can causehearing loss if one is exposedto them over long periods oftime. 10
    11. 11. What are the primary tastesensations, and how are theydetected? 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 11
    12. 12. What are the primary tastesensations, and how are theydetected?  Taste sensations are detected by receptor cells in the taste buds  Specialized receptors are activated by each flavor (sweet, sour, etc.) 12 – These receptors send separate messages to the brain
    13. 13. The Skin Senses Include the senses of touch and pain These senses are critical for survival 13
    14. 14. How does the skin providesensory 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 14
    15. 15. What is the function of pain, and how ispain 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 15
    16. 16. 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 16
    17. 17. What is gained and what is lostin 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 17
    18. 18. How does prior knowledgeinfluence 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 18
    19. 19. Principles of Perception A few principles govern perceptions in all humans 19
    20. 20. What are the principles that governperceptual 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 20 – Closure: Figures with gaps in them are perceived as complete
    21. 21. How does the brain perceivemotion? 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 21
    22. 22. What are three types ofpuzzling 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 22
    23. 23. What are three types ofpuzzling 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 23
    24. 24. Unusual PerceptualExperiences 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 24
    25. 25. In what ways does subliminalperception 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 25
    26. 26. What have studies of ESPshown? 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 26
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