phycologykfupmFeldmanEUP11e_PPT_Ch03(1).pptx

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Chapter 3
Sensation and
Perception

3-2
MODULE 8 - Sensing the World Around
Us
• What is sensation, and how do psychologists
study it?
• What is the relationship between a physical
stimulus and the kinds of sensory responses that
result from it?

3-3
Introduction
• Sensation: Activation of the sense organs by a
source of physical energy
• Perception: Sorting out, interpretation,
analysis, and integration of stimuli
• Carried out by the sense organs and brain

3-4
Introduction
• Stimulus: Energy that produces a response in a
sense organ
• Psychophysics: Study of the relationship
between:
• Physical aspects of stimuli and our psychological
experience of them

3-5
Absolute Thresholds: Detecting What’s
Out There
• Absolute threshold: Smallest intensity of a
stimulus that must be present for it to be
detected
• Noise - Background stimulation that interferes
with the perception of other stimuli

3-6
Difference Thresholds: Noticing
Distinctions Between Stimuli
• Difference threshold: Smallest level of added
or reduced stimulation
• Required to sense that a change in stimulation
has occurred
• Just noticeable difference
• Weber’s law: Just noticeable difference is a
constant proportion of the intensity of an initial
stimulus

3-7
Sensory Adaptation: Turning Down Our
Responses
• Adaptation: Adjustment in sensory capacity
after prolonged exposure to unchanging stimuli
• Decline in sensitivity to sensory stimuli
• Inability of the sensory nerve receptors to fire off
messages to the brain indefinitely

3-8
MODULE 9 - Vision: Shedding Light on
the Eye
• What basic processes underlie the sense of
vision?
• How do we see colors?

3-9
Figure 1 - The Visible Spectrum

3-10
Illuminating the Structure of the Eye
• Cornea - Transparent, protective window
• Refracts light
• Pupil - Dark hole in the center of the iris , the
colored part of the eye
• Opening depends on amount of light in
environment
• Light enters the lens after passing through the
pupil
• Accommodation - Process of, lens focusing light
by changing its own thickness

3-11
Figure 3 - Basic Cells of the Eye

3-12
• Retina: Part of the eye that converts the
electromagnetic energy of light to electrical
impulses for transmission to the brain
• Includes light-sensitive receptor cells
• Rods: Thin, cylindrical receptor cells that are highly
sensitive to light
• Cones: Cone-shaped receptor cells responsible for
sharp focus and color perception, particularly in
bright light
• Concentrated in the fovea

3-13
• Rods and cones are involved in dark adaptation
• Phenomenon of adjusting to dim light after being in
brighter light
• Peripheral vision
• Seeing objects that are outside the main center of
focus

3-14
• When light strikes the retina:
Stimulation
of the nerve
cells
triggers a
neural
response
Reaches
the rods
Receive
information
directly
from the
rods and
cones
Bipolar
cells
Collect and
summarize
visual
information
Ganglion
cells
Carries
visual
information
to the brain
Optic
nerve

3-15
• Processing the visual message
• Takes place in the visual cortex of the brain
• Feature detection: Specialized neurons that are
activated only by visual stimuli having specific
features
• Particular shape or pattern

3-16
Color Vision and Color Blindness: The
Seven-Million-Color Spectrum
• Trichromatic theory of color vision
• Suggests that there are three kinds of cones in the
retina each of which responds primarily to a
specific range of wavelengths
• Afterimage - Occurs because activity in the retina
continues even when you are no longer staring at
the original picture

3-17
Color Vision and Color Blindness: The
Seven-Million-Color Spectrum
• Opponent-process theory of color vision
• Receptor cells are linked in pairs, working in
opposition to each other

3-18
MODULE 10 - Hearing and the Other
Senses
• What role does the ear play in the senses of
sound, motion, and balance?
• How do smell and taste function?
• What are the skin senses, and how do they relate
to the experience of pain?

3-19
Sensing Sound
• Sound: Movement of air molecules brought
about by a source of vibration
• Eardrum: Part of the ear that vibrates when
sound waves hit it
• Vibrations are then transferred into the middle ear
containing three bones
• Hammer, anvil, stirrup

3-20
Sensing Sound
• Inner ear - Changes the sound vibrations into a
form transmittable to the brain
• Cochlea: Coiled tube in the ear filled with fluid that
vibrates in response to sound
• Basilar membrane: Contains sense receptors for
sound
• Hair cells: Tiny cells covering the basilar
membrane that, when bent by vibrations entering
the cochlea, transmit neural messages to the brain

3-21
Figure 1 - The Ear

3-22
Sensing Sound
• Physical aspects of sound
• Frequency - Number of wave cycles that occur in
a second
• Pitch - Makes sound seem “high” or “low”
• Amplitude - Wave patterns that help in
distinguishing loud and soft sounds
• Decibels - Range between the strongest and
weakest sounds that can be heard

3-23
Sensing Sound
• Sorting out theories of sound
• Place theory of hearing: Different areas of the
basilar membrane respond to different
frequencies
• Provides explanation for the sensing of high-
frequency sounds
• Frequency theory of hearing: Entire basilar
membrane vibrates as a whole in response to a
sound
• Explains what happens when low-frequency sounds
are encountered

3-24
Sensing Sound Balance: The Ups and
Downs of Life
• Vestibular system - Formed by semicircular
canals
• Semicircular canals: Three tube-like structures
of the inner ear containing fluid that sloshes
through them when the head moves, signaling
rotational or angular movement to the brain
• Otoliths - Tiny, motion-sensitive crystals in the
semicircular canals
• Senses forward, backward, or up-and-down motion,
as well as the pull of gravity

3-25
Smell
• Olfaction
• Sense of smell is sparked when the molecules of a
substance enter the nasal passages
• Olfactory cells - Receptor neurons of the nose
• Pheromones - Chemicals secreted into the
environment
• Produce a reaction in other members of the same
species

3-26
Taste
• Gustation - Sense of taste
• Respond to basic stimulus qualities:
• Sweet
• Sour
• Salty
• Bitter
• “Umami”
• Taste buds
• Supertasters - Sensitive to taste
• Nontasters - Insensitive to taste

3-27
The Skin Senses: Touch, Pressure,
Temperature, and Pain
• Skin senses: Touch, pressure, temperature,
and pain
• Operate through nerve receptor cells located at
various depths throughout the skin
• Pain - Extensively researched skin sense
• Susceptibility to pain is different from person to person
• Substance P - Transmits pain messages to the brain
• Gate-control theory of pain: Particular nerve
receptors in the spinal cord lead to specific areas
of the brain related to pain

3-28
How Our Senses Interact
• Synesthesia - Exposure to one sensation evokes
an additional one
• Multimodal perception - Brain collects the
information from the individual sensory
systems:
• Integrates and coordinates the information

3-29
MODULE 11 - Perceptual Organization:
Constructing Our View of the World
• What principles underlie our organization of the
visual world and allow us to make sense of our
environment?
• How are we able to perceive the world in three
dimensions when our retinas are capable of
sensing only two-dimensional images?
• What clues do visual illusions give us about our
understanding of general perceptual
mechanisms?

3-30
The Gestalt Laws of Organization
• Series of principles that describe how we
organize bits and pieces of information into
meaningful wholes

3-31
Figure 2 - Organizing Various Pieces of
Information into Meaningful Wholes

3-32
Top-Down and Bottom-Up Processing
• Top-down processing: Perception is guided
by:
• Higher-level knowledge
• Experience
• Expectations
• Motivations
• Bottom-up processing: Progression of
recognizing and processing information from:
• Individual components of a stimuli and moving to
the perception of the whole

3-33
Depth Perception
• Ability to view the world in three dimensions
and to perceive distance
• Binocular disparity - Difference in the images
seen by the left eye and the right eye

3-34
Depth Perception
• Monocular cues - Permit us to obtain a sense of
depth and distance with just one eye
• Motion parallax
• Relative size
• Texture gradient
• Linear perspective

3-35
Perceptual Constancy
• Physical objects are unvarying and consistent
even though sensory input about them may vary
• Allows to view objects as having an unchanging
size, shape, color, and brightness
• Even if the image on our retina changes

3-36
Motion Perception: As the World Turns
• Cues about perception of motion
• Movement of an object across the retina is
perceived relative to some stable background
• Movement of images across the retina

3-37
Motion Perception: As the World Turns
• Factor information about our own:
• Head and eye movements
• Information about changes in the retinal image
• Apparent movement - Perception that a
stationary object is moving

3-38
Perceptual Illusions: The Deceptions of
Perceptions
• Visual illusions: Physical stimuli that
consistently produce errors in perception
• Cultural differences are reflected in depth
perception

3-39
Figure 6 - Müller-Lyer Illusion

3-40
Subliminal Perception
 Perception of messages about which we have no
awareness
 Referred as priming by sociologists
 Stimulus could be a:
 Written word
 Sound
 Smell

3-41
Extrasensory Perception (ESP)
senses
• Psychologists reject the existence of ESP asserting
that:
• There is no sound documentation of the
phenomenon
• Psychological bulletin
• Anomalous process of information transfer or psi

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