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

threshold2. Sometimes we know more than

we think we do3. 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）

Purity Saturation （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

Frequency Pitch

amplitude Loudness

Complexity Timbre

How do we perceive pitch

Place theory — high-pitched sounds

Frequency theory — low-pitched

volley principleConduction deafnessNerve 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