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Chapter 5 Sensation — the window on the world How does the world out there get in?
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Sensation and Perception Sensation: the process by which stimuli are detected and encoded, enabling us to experience a ping pang as a moving, white object Perception: the mental process of organizing and interpreting our sensation, enabling us to see not just moving whiteness, but a ping pang.
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The Definition Sensation — the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment (bottom-up) Perception — the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events (top-down)
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Sensing the World: Some Basic Principles Sensation depends on specialized cell called sensory receptors which detect stimuli and convert their energy into neural impulses. This process is called sensory transduction — the process by which sensory receptors convert stimuli (physical, chemical energy) into neural impulses.
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Thresholds (阈限) Psychophysics: the study of relationships between the physical characteristics of stimuli, such as their intensity, and psychological experience of them Absolute threshold: the minimum stimulation needed to detect a particular stimulus Signal detection theory: AT vary, not only on the signals strength, but also our psychological state ……
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Does Subliminal Stimulation Work? Yes 1. The definition of absolute threshold 2. Sometimes we know more than we think we do 3. The experiment No no powerful, enduring effect on behavior
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Difference threshold — just noticeable difference jnd: the minimum difference that a subject can detect between two stimuli 50 percent of the time Weber ’ s Law: I/I=k I: intensity pitch-1/333; weight-1/50; taste-1/5
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Sensory Adaptation—diminished sensitivity as a consequence of constant stimulation The experiment ( p.235 ;中文 p.163 ) An important benefit — it enables us to focus our attention on informative changes in our environment without being distracted by the uninformative constant stimulation of garments, odors, and street noise. Some exceptions: dark, and pain
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Vision Physical characteristics of light Sensory experience wavelength Hue (色调) Intensity (wave ’ s amplitude) Brightness (亮度) PuritySaturation (饱和度)
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Localization of function in the brain Artificially route visual information to the brain, thus restoring sight in the blind “ Seeing ” does not take place in the eyes, so to hearing, smelling …… Seeing involves the entire eye-brain system
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Visual Information Processing Feature detection (p. 241) Parallel processing (p.242) — our brains do many things at once, automatically and without our awareness
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Color vision—if no one sees the tomato, is it red? Young-Helmoholtz trichromatic (three-color) theory Thomas Young, an English physicist (1802) Helmoholtz (1857) — they inferred that the eye must have three types of receptors, one for each primary color of light Cannot explain r-g color blindness
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Color Mixing—additive and subtractive
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Opponent-process theory Ewald Hering (physiologist, 1870) Afterimage There were 2 additional color processes, one responsible for red vs. green perception, and one for blue vs. yellow. Reconciling theories of color vision
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Hearing Physical characteristics of sound Sensory experience FrequencyPitch amplitudeLoudness ComplexityTimbre
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How do we perceive pitch Place theory — high-pitched sounds Frequency theory — low- pitched volley principle Conduction deafness Nerve deafness
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Pain Born without the ability to feel ~ Those who endure chronic ~ What is pain? phantom limb pain — to see, hear, and feel, we require not a body but a brain
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Gate Control Theory (R. Melzack & Patrick wall, 1965, 1983) The spinal cord contains a neurological “ gate ” that blocks pain signals or allows them pass on to the brain. The activity of pain signals traveling up small nerve fibers — open Activity in larger fibers or information comes from brain — close
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Understanding Pain
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Pain Control—it is indeed a physical and a psychological phenomenon Anxiety Attention — distraction, counterirrtation Control Interpretation (cognitive strategies) Application
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Interaction of the sense Synesthesia ……
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Sensory Restriction or Deprivation Disoriented, experience hallucinations? Or it reduces stress and helps people become more open to positive influence? Foster our fulfillment? REST — restricted environmental stimulation therapy
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