Chapter 5 Sensation — the window on the world How does the world out there get in?

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.

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)

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.

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 ……

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

 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

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

Vision Physical characteristics of light Sensory experience wavelength Hue （色调） Intensity (wave ’ s amplitude) Brightness （亮度） PuritySaturation （饱和度）

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

Visual Information Processing  Feature detection (p. 241)  Parallel processing (p.242) — our brains do many things at once, automatically and without our awareness

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

Color Mixing—additive and subtractive

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

Hearing Physical characteristics of sound Sensory experience FrequencyPitch amplitudeLoudness ComplexityTimbre

How do we perceive pitch  Place theory — high-pitched sounds  Frequency theory — low- pitched  volley principle  Conduction deafness  Nerve deafness

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

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

Understanding Pain

Pain Control—it is indeed a physical and a psychological phenomenon  Anxiety  Attention — distraction, counterirrtation  Control  Interpretation (cognitive strategies) Application

Interaction of the sense  Synesthesia  ……

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