PSYCHOLOGY IN ACTION
Sixth Edition
by
Karen Huffman
PowerPoint  Lecture Notes Presentation
Chapter 4
Sensation & Perception
Paul J. Wellman
Texas A&M University
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Lecture Overview
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Experiencing Sensations
Vision
Other Senses
Perception
– Selection
– Organization
– Interpretation
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Sensation and Perception
• Sensation is the process of receiving,
converting, and transmitting information from the
outside world
– Sensory organs contain receptors that transduce
sensory energy into nerve impulses that are carried to
the brain
• Perception involves organization and
interpretation of sensory input
– Interpretation of sensory input is an active process
– Perceptions can differ among people
• Top-down processing versus bottom-up
processing
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Sensation/Perception
• Transduction: sensory receptors convert
a physical energy into nerve impulses
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Sensory Thresholds
• Each sensory system has a threshold level of
energy that is required to activate that sense
– Absolute threshold: The smallest amount of energy
that can be detected by a system
– Difference threshold: The smallest difference in
sensory energies that can be detected
• Different people can have widely varying
sensory thresholds
• Thresholds can change within a person over
time and as a function of hormone status
– Olfactory sensitivity during pregnancy
– Ability to taste foods as we get older
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Modification of Sensation
• A key function of sensory systems is to detect
change within the environment
– Movement in the peripheral aspects of the eye may
signal food or danger
– Constant pressure of an object on the skin may not be
important
• A stimulus that moves across the skin may be a snake or a
spider
• The skin adapts to constant pressure
– Constant pain is unpleasant and wastes body
resources
• Pain is offset by a control system involving opiates
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Vision
• External light falls on receptors within the
eye to generate the visual message
• Light = electromagnetic radiation
– Wavelength of light determines color
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Anatomy of the Eye
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Photoreceptors
• Photoreceptors are light-sensitive cells
found within the retina
– Rods are sensitive to light, but not color,
and are active under low-light conditions
– Cones are sensitive to color, are not active
in low-light conditions, and allow for fine
detail
– Rods and cones use different
photopigments that react to light so as to
generate nerve potentials
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Retinal Photoreceptors
• Light passes through the
retinal layers to reach the
photoreceptors at the inner
retinal surface
• Photoreceptors and bipolar
cells conduct potentials to
the ganglion cells, which in
turn initiate action potentials
which are transmitted to the
thalamus
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Sensory Coding
• Activation of retinal
cells by light results
in action potentials
that travel along
neurons that project
to the occipital cortex
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Hearing
• Receptors within the ear are tuned to
detect sound waves (changes in sound
pressure level)
– Sound waves vary in terms of
• Frequency: corresponds to pitch
• Amplitude: corresponds to loudness
• Sound loudness is measured in
decibels
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Sound Loudness (dB)
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Anatomy of the Ear
(Sound Waves)
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Pitch and Loudness
• Sound waves vibrate the basilar
membrane within the cochlea of the ear
– Hair cells containing receptors bend in
response to vibration of the membrane
– Hair cells trigger action potentials that are
carried to the auditory cortex
– Different frequencies produce maximal
vibration of different areas along the
membrane: produces place coding of pitch
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Perception
• Perceptual processes
include
– Selection refers to choosing
which of many stimuli that will
be processed
– Organization involves
collecting the information into
some pattern
– Interpretation involves
understanding the pattern
• Perceptions can be in error
– Illusions are visual stimuli
that are misinterpreted
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Horizontal-Vertical Illusion
WHICH LINE IS LONGER?
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Form Perception
• Figure and background are basic
organizational themes for perception
• Gestalt psychologists examined
properties that make for a good figure
– Figure is perceived as distinct from the
background
– Figure is closer to the viewer than the
background
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Gestalt Organizational Principles
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Color Perception
• Humans are able to discriminate 7 million
different hues
• Colors convey important information
– Ripeness of food
– Danger signals (traffic lights; for some people…)
• Trichromatic theory
– Eye contains 3 different color sensitive elements
• Blue, green or red elements
• Trichromatic theory accounts for color mixing of lights
• Opponent-Process theory
– Visual system is organized into red-green, blueyellow and black-white units
• Theory can account for negative color afterimages
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Extrasensory Perception
• ESP refers to the ability to perceive
stimuli that are outside the 5 senses
– Telepathy: the ability to read minds
– Clairvoyance: the ability to perceive objects
or events
– Precognition: the ability to predict the future
– Psychokinesis: the ability to move objects
© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E
Copyright
Copyright 2002 by John Wiley & Sons, Inc., New
York, NY. All rights reserved. No part of the material
protected by this copyright may be reproduced or
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© 2002 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 6E