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COURSE NOTES: Introductory Psychology

Psych101 graphic

Chapter 5:

Sensation and Perception

Notes for Psychology 101: based on Myers's text, Exploring Psychology, with supplements and modifications by the instructor, Prof. Cloninger.

term denotes a term that you should know how to define, and to recognize and give examples.

person denotes an important person. You should remember this person's name and what (s)he has done.

findingdenotes an important research finding.

issuedenotes an issue that you should be able to discuss or explain.


Notes for Psychology 101

(based on Myers Exploring Psychology, with supplements and modifications by the instructor, S. Cloninger)

termSENSATION
  • detecting physical energy from the environment and encoding it as neural signals
    example: hearing a sound; seeing a light

termPERCEPTION

  • selecting, organizing, and interpreting our sensations
  • examples: identifying the sound as a phone ringing; identifying the light as a star

What is primary--sensations? expectations?

  • termBottom-up processing (starts with sensory analysis)
  • light, sound waves, etc.
  • termTop-down processing (starts with experience and expectations)
  • brain

Prosopagnosia: inability to consciously perceive faces (temporal lobe damage)

  • Some patients with brain damage can see but don't recognize their family.

SENSING THE WORLD: SOME BASIC PRINCIPLES

THRESHOLDS

termPsychophysics: the study of how physical energy (such as sound waves) relates to psychological experience (such as hearing)
termAbsolute threshold: the minimum stimulation necessary to detect a particular stimulus 50% of the time

termsubliminal stimuli: stimuli below the absolute threshold

  • example: "EAT POPCORN"

What about detecting changes?

  • Detecting differences in stimuli
  • termDifference threshold (jnd)
  • "just noticeable difference"
    • Adding a pound to a 1 pound weight is much more noticeable than adding that pound to a 100 pound weight.
  • Weber's law (sensitivity to change): the jnd is a constant proportion of the stimulus, for a given stimulus
    • 8/100 for light intensity
    • 2/100 for weight
    • 3/1000 for pitch

termSENSORY ADAPTATION: diminishing sensitivity to an unchanging stimulus

  • example: don't notice a constant background noise

Psychophysics can describe the relationship between the physical stimulus and our awareness of it, but to know the mechanisms, we turn to neuroscience.

  • [lecture image: receptors for the various senses where physical energy is converted into neural impulses]

VISION

Our "visual field" extends 90 degrees left and right, 60 degrees up, and 75 degrees down. [lecture image]

THE STIMULUS INPUT: LIGHT ENERGY

Electromagnetic spectrum

Some facts about light:

  • Light consists of electromagnetic energy about 400 to 700 nanometers (nm).
  • One nanometer is one billionth of a meter.
  • The wave of light reflected from a book you are reading have wiggled back and forth about a million times before reaching your eyes.

Light Stimuli and Psychological Effects

  • wavelength produces color (short: blue; long: red)
  • wave amplitude produces brightness (intensity) (high amplitude: bright)

Visible spectrum (to humans): from long red waves to short violet waves

  • memory trick: "ROY G. BIV"
  • red, orange, yellow, green, blue, indigo, violet
  • Can you tell the difference between indigo and violet?

THE EYE

Iris

Lens

  • Accommodation

Retina

  • Technically, the retina is actually part of the brain!

Receptors:

  • termRods (120 million black-white receptors, for dim light and peripheral vision)
  • termCones (6 million color receptors, for bright light and vision in center of field)

rods vs. cones

  • Owls and other nocturnal animals have few cones.
  • Lizards and other animals active during the day have few rods.
  • Colors are harder to see at night (with cones).
  • Rods are very sensitive. The light emitted by one candle 30 miles away is enough to produce a visual response!

Second level:

termBipolar cells

Third level:

Ganglion cells

termOptic nerve

termBlind spot


VISUAL INFORMATION PROCESSING

Feature detection

termFeature detectors for particular edges, lines, angles, and movements (Hubel & Wiesel)

Parallel processing

  • The brain makes several calculations at once (color, motion, form, depth, etc.: none of these necessarily precedes the others, or depends on the others)
  • blindsight

COLOR VISION


personYoung-Helmholtz termtrichromatic theory

3 types of color receptors (red, green, blue)

personHering's termopponent-process theory

Red-green and yellow-blue
termAfterimages [graphic illustrations in lecture]

In additive color mixture,

  • RED + GREEN = YELLOW
  • YELLOW + BLUE = WHITE

subtractive color mixture

  • paint is subtractive
  • Yellow absorbs short wave lengths; blue absorbs long wave lengths; what remains is about 500 nm, which appears green.

To a color-blind person

  • red, orange, yellow, and green may all look the same.
  • "red" cherries on a tree look the same color as the (green) leaves.

7-8% of males have some deficiency in color vision..

  • usually red-green
  • rarely blue-yellow

Red and green are distinguished only in humans and other higher primates. Most mammals have only 2 types of cones.

  • So, we can tell a ripe apple from a green one, but most animals can't. Cool.

termColor constancy

  • Context, or surrounding objects, is taken into account to produce constancy or, on the other hand, contrast

termsimultaneous contrast (brightness; hue) [graphic illustrations in lecture]


THE OTHER SENSES

HEARING

Audition (hearing)

The Stimulus Input: Sound Waves

  • wave frequency (wavelength) produces pitch
  • wave amplitude produces loudness
    • Sound energy is measured in decibels

The Ear

Auditory canal

Eardrum

Middle ear

  • Hammer, anvil, stirrup

Inner ear

  • termCochlea
  • Oval window
  • termBasilar membrane
  • Hair cells

findingLoud sounds can cause physical damage to the ear.

findingHearing loss also occurs with age, especially for higher frequencies.

How Do We Locate Sounds?

  • Intensity and timing signals to 2 ears


TOUCH

Basic four skin senses:

  • Pressure
  • Warmth
  • Cold
  • Pain

PAIN

Signal of something wrong

Chronic pain

termPhantom limb sensations

termGate-control theory of pain (Melzack & Wall)

  • close gate by stimulating large neural fibers

Pain control

  • Lamaze method of childbirth
  • Relaxation
  • Counterstimulation
  • Distraction

TASTE

a chemical sense

4 basic sensations:

  • sweet, sour, salty, bitter

taste buds

termsensory interaction: one sense (smell) may influence another (taste)


SMELL

olfaction
a chemical sense
shape of odor molecules
primitive
associated with memory and emotions


BODY POSITION AND MOVEMENT

termKinesthesis: the sense of our body parts' position and movement

termVestibular sense: monitors position and movement of the head

  • In the ear, semicircular canals and vestibular sacs (connecting to cochlea)


PERCEPTUAL ORGANIZATION

gestalt: an organized whole

termFORM PERCEPTION

termFigure and Ground

Grouping

  • Proximity
  • Similarity
  • Continuity
  • Connectedness
  • Closure

[several graphic images are presented in class]

  • "Weeping Willow" puzzle (1795)
  • figure/ground (ambiguous figure)
    • Did you see an urn, or two faces?
  • Dali (notice the figure-ground effect)
  • The "Devil's Triangle"
    • one way to build the devil's triangle (viewed from one angle only!)
  • Necker cube
  • subjective triangles
    • You say there are triangles in that image? Really?

termDEPTH PERCEPTION

3-dimensional world

termvisual cliff (Gibson & Walk)

termbinocular cues to depth

  • termretinal disparity
    • DEMO: point to a corner of the ceiling. Cover one eye, then the other.
  • termconvergence
    • DEMO: move your finger toward your eyes.

monocular cues to depth

  • relative size
  • interposition
  • relative height
  • termrelative motion (motion parallax)
  • termlinear perspective
  • relative brightness


termPERCEPTUAL CONSTANCY

Objects are perceived as unchanging

termShape constancy

termSize constancy

termSize-distance relationship

Objects appear larger, despite similar retinal size, if they are perceived as farther away.

  • Moon illusion (appears larger on horizon)

Other illusions

  • Ponzo illusion
  • Muller-Lyer illusion
  • Ames room

Lightness constancy (brightness constancy)

  • relative luminance (reflection of light)

Perceptual Interpretation

Nature (Kant) or nurture (Locke)?

SENSORY DEPRIVATION AND RESTORED VISION

Cases of restored sight (e.g., cataracts present since birth were removed):

innate awareness of figure-ground and of color, but impaired ability to visually recognize objects (known previously by touch)

critical period for normal sensory and perceptual development


termPERCEPTUAL ADAPTATION

Distorting lenses

  • can make image appear several degrees to left (or right)
  • People adapt; chickens do not

Stratton's inverting lenses


termPERCEPTUAL SET

Expectations influence what is perceived.

  • Example: Loch Ness monster photo
  • Example: hidden lyrics in songs

Context effects


THINKING CRITICALLY ABOUT: EXTRASENSORY PERCEPTION

termExtrasensory perception (ESP)

parapsychologists

CLAIMS OF ESP

Telepathy

Clairvoyance

Precognition

PREMONITIONS OR PRETENSIONS

PUTTING ESP TO EXPERIMENTAL TEST

  • Experimental tests do not validate ESP claims.

personJames Randi's challenge

Thinking critically about ESP

Ongoing studies using the ganzfeld procedure to produce sensory deprivation, claimed to be conducive to telepathy; controversy and research continue.


Students: You can also use resources for this text supplied by the publisher. These include a chapter overview, self-tests, and other resources.


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Some images are from "Holy Cow! 250,000 Graphics,"
© by Macmillan Digital Publishing USA.
Ch. 1: Introduction
Ch. 2: Neuroscience
Ch. 3: Nature & Nurture
Ch. 4: Development
Ch. 5: Sensation & Perception
Ch. 6: Consciousness
Ch. 7: Learning
Ch. 8: Memory
Ch. 9: Thinking
Ch. 10: Motivation
Ch. 11: Emotion
Ch. 12: Personality
Ch. 13: Disorders
Ch. 14: Therapy
Ch. 15: Social
additional notes