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Ch. 3 - Sensation and Perception
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Sensation - The experience of sensory
stimulation
Perception - The process of creating
meaningful patterns from raw sensory
information
1.
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The Nature of Sensory Processes
A. The Basic Process
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Receptor Cell- A specialized cell that responds to a
particular type of energy
B. Sensory Thresholds
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Absolute
 The least amount of energy that can be detected
50% of the time
Adaptation
 An adjustment of the senses to the level of
stimulation
Sensory Thresholds
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Difference
 The smallest change in stimulation that can be
detected 50 % of the time
Subliminal perception
 Below our level of awareness
Extrasensory perception
 Extraordinary perception such as sensing the
future
2. Vision
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A. The Visual System
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Cornea
 transparent protective coating over the front of the
eye
Pupil
 small opening in the iris through which light enters
the eye
Iris
 colored part of the eye
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Lens
 transparent structure inside the pupil that focuses
light onto the retina
Retina
 lining of the eye containing receptor cells that are
sensitive to light
Retina Movie
The Visual System
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Visual System Movie
#1
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Visual System Movie
#2
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Visual System Movie
#3
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Receptor cells
 Wavelengths - different energies represented in
the electromagnetic spectrum
 Rods - receptor cells in the retina for night vision
 Cones - receptor cells in the retina responsible for
color vision.
 Bipolar Cells - connect receptors to ganglion
 Fovea / visual acuity - area of the retina with the
sharpest vision
Retina / Fovea Movie
Cones respond to light and dark as well as
to color or different wavelengths of light
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Adaptation
 Dark
 Increased sensitivity of rods and cones in
darkness
 Light
 Decreased sensitivity of rods and cones in
bright light
 Afterimage
 Sense experience that occurs after a visual
stimulus has been removed
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Eye to brain
 Neurons that connect the bipolar cells in the eyes
to the brain
 Optic nerve are bundle of axons of ganglion cells
that carries neural messages from each eye
 Blind spot
 place where the axons of all the cells leave the
retina (no receptors)
The bipolar cells connect to ganglion cells,
whose axons converge to form the optic nerve
that carries messages to the brain
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B. Color Vision
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Properties of color
 Hues – Colors such as red and green
 Saturation - Vividness of a hue
 Brightness - Nearness of a color to white
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Theories of color vision
 Subtractive color
 Mixing pigments
 Additive color mixing
 Lights, T.V., monitor (RGB)
 Trichromatic
theory (Helmholtz)
 Colorblindness (Tri-,Di-, and
Monochromats)
 3 different receptors (RGB)
 People inherit receptors which respond
differently
 Opponent-process
theory (Hering)
 Three sets of color receptors
 Yellow-blue, red-green, black-white
 Either/or response
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C. Color Vision in Other Species
The opponent-process theory maintains that receptors are
specialized to respond to either member of the three basic color pairs:
red-green, yellow-blue, and black-white (dark and light)
3. Hearing
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A. Sound
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Sound waves
 Changes in pressure caused by molecules of air
moving
Frequency
 Number of cycles per second in a wave; pitch
Hertz
 Cycles per second; frequency
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Pitch
 Frequency of vibrations, results in tone
Amplitude
 Magnitude; loudness
Decibels
 Measurement of loudness
Overtones - Multiples of the basic tone
Timbre - Quality of texture of sound
Amplitude is the magnitude of a wave; it
largely determines the loudness of a sound.
Loudness is measured in decibels
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B. The Ear
Hammer, anvil, stirrup
 3 small bones in the middle ear that relay
vibrations
 Oval window
 Membrane between middle ear and inner ear
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Hearing begins when sound waves strike the eardrum and
cause it to vibrate. This vibration, in turn, makes three
bones in the middle ear—the hammer, the anvil, and the
stirrup—vibrate in sequence
Cochlea
 Part of inner ear containing fluid that vibrates
and then causes the basilar membrane to
vibrate
 Basilar membrane
 Vibrating membrane in the cochlea which
contains receptor cells
 Neural connections
 Auditory nerve
 Connection from ear to brain
 Bilateral
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Inside the organ of Corti are tiny hair cells that act as sensory
receptors for hearing. Stimulation of these receptors produces auditory
signals that are transmitted to the brain through the auditory nerve.
The brain pools the information from thousands of these cells to create
the perception of sounds
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C. Theories of Hearing
Place theory
 Pitch is determined by location of vibration
 Frequency theory
 Pitch is determined by frequency hair cells fire
 Volley Principle
 Pattern of sequential firing determines pitch
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Hearing disorders
 Damaged eardrum
 Damaged middle ear bones
 Damaged nerves
 Loud music, tools, etc
 Tinnitus 1% of population
4. The Other Senses
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A. Smell
Detecting common odors
 Communicating with pheromones
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B. Taste
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Receptor cells in taste buds
The sense of smell is activated by substances carried by
airborne molecules into the nasal cavities, where the
substances activate highly specialized receptors for smell,
located in the olfactory epithelium
The receptor cells for the sense of taste are
housed in the taste buds on the tongue, which, in
turn, are found in the papillae, the small bumps
on the surface of the tongue
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C. Kinesthetic and Vestibular Senses
Stretch receptors
 Sense muscle stretch and contraction
 Golgi tendon organs (injections)
 Sense movement of tendons
 Vestibular senses
 Senses of equilibrium and body position
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D. Sensations of Motion
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Vestibular organs are also responsible for motion
sickness
 May be caused by discrepancies between visual
information and vestibular sensation
E. The Skin Senses
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Skin receptors for pressure, temperature, and pain
Importance of touch
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F. Pain
 Individual differences
 Gate control theory
 Gate
in spinal cord which controls transmission of
pain to brain
 Biopsychosocial
theory
 The Placebo Effect
 Alternative approaches
5. Perception
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A. Perceptual Organization
B. Perceptual Constancies
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Size constancy
Shape constancy
Brightness constancy
Color constancy
Perceptual Organization
Perceptual constancy is our tendency to perceive objects
as unchanging in the face of changes in sensory
stimulation. Once we have formed a stable perception of
an object, we can recognize it from almost any angle
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C. Perception of Distance and Depth
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Moon Movie
D. Perception of Movement
E. Visual Illusions
When we use sensory information to create perceptions,
we fill in the missing information, group various objects
together, see whole objects, and hear meaningful sounds
Visual illusions occur when we use a
variety of sensory cues to create perceptual
experiences that do not actually exist
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F. Observer Characteristics: Individual
Differences and Culture Motivation
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Value
Expectation
Cognitive Style
Experience and Culture
Personality
Superposition is a monocular distance cue
in which one object, by partly blocking a
second, appears closer
Linear perspective is another monocular cue to distance
and depth based on the fact that two parallel lines seem to
come together at the horizon