CHAPTER 3 – SENSATION AND PERCEPTION
MODULE 3.1 SENSING OUR WORLD: BASIC CONCEPTS OF SENSATION
After you have mastered the information in this unit, you will be able to:
 Describe sensation
 Explain the difference between absolute thresholds and difference thresholds
 Discuss the factors that contribute to signal detection
 Define sensory adaptation
Key Terms and Concepts:
Sensation
Sensory Receptors
Psychophysics
Absolute Threshold
Difference Threshold
Weber’s Law
Signal-Detection Theory
Sensory Adaptation
I.
II.
III.
IV.
Sensation
A.
Process by which we receive, transform, and process stimuli presented to sensory organs
B.
Sensory receptors—in sensory organs
1.
Detect stimuli from the outside world
2.
Very sensitive to certain types of stimuli
3.
Form of light, sound, odors, etc.
C.
Psychophysics—how we experience such stimuli
Absolute and Difference Thresholds
A.
Absolute threshold
1.
Smallest amount of stimulus reliably detected
2.
Variation in sensitivity among individuals
B.
Difference threshold
1.
Just-noticeable difference (jnd)
2.
Weber’s law—must change stimulus by a constant proportion for change to be
detected
3.
Constants are given for various senses
Signal Detection
A.
Signals are stimuli such as sounds or tastes
B.
Detection depends on
1.
Intensity of signal
2.
Background factors
3.
Attention and motivation of receiver
4.
Physical condition of organism
Sensory Adaptation—becoming less sensitive to unchanging stimuli
MODULE 3.2 VISION: SEEING THE LIGHT
After you have mastered the information in this unit, you will be able to:
 Explain how the eye processes light
 Identify feature detectors and describe their role in visual processing
 Discuss the two major theories of color vision
 Identify the two major forms of color blindness
Key Terms and Concepts:
Cornea
Iris
Pupil
Lens
Accommodation
Retina
Photoreceptors
Rods
Cones
Bipolar Cells
Ganglion Cells
Optic Nerve
Blind Spot
Fovea
Feature Detectors
Trichromatic Theory
Afterimage
Opponent-Process Theory
Trichromats
Monochromats
Dichromats
I.
II.
III.
IV.
Light: The Energy of Vision
A.
Physical energy
B.
Electromagnetic radiation
1.
Visible spectrum is small portion of entire spectrum
2.
Wavelengths correspond to the experience of different colors
The Eye: The Visionary Sensory Organ
A.
Contains the sensory receptors to detect light
B.
Parts of the eye
1.
Cornea—transparent covering on the surface of the eye
2.
Iris—muscle surrounding pupil
a.
Adjusts reflexively to permit entry of light
b.
Colored part of eye, usually blue or brown
3.
Pupil—size of opening is controlled by iris
4.
Lens—changes shape to adjust to distance of object (accommodation)
5.
Retina
a.
Receives the image created by light striking it
b.
Contains photoreceptors—rods and cones
6.
Bipolar cells—interconnecting cells
7.
Ganglion cells—each projecting axon is one nerve fiber
8.
Optic nerve
a.
Large bundle of ganglion nerve fibers
b.
Transmits visual information to the brain
c.
Creates blind spot
9.
Fovea—part of the retina
a.
Contains only cones
b.
Site for sharpest vision
Feature Detectors: Getting Down to Basics
A.
Nerve cells in visual cortex
B.
Respond to specific features of the visual stimulus
Color Vision: Sensing a Colorful World
A.
Color receptors (cones) transmit different messages to the brain
B.
Hermann von Helmholtz—trichromatic theory
1.
Three types of color receptors—for red, green, and blue-violet
2.
Other colors result from combinations of these three
C.
Ewald Hering—opponent-process theory
1.
Afterimages—image seen on neutral surface after other visual stimulation
2.
Three sets of color receptors that work in either-or pairs
MODULE 3.3 HEARING: THE MUSIC OF SOUND
After you have mastered the information in this unit, you will be able to:
 Discuss how the ear enables us to hear sound
 Explain what determines our perception of pitch
 Describe the main types and causes of deafness
Key Terms and Concepts:
Audition
Pitch
Eardrum
Ossicles
Oval Window
Cochlea
Basilar Membrain
Organ of Corti
Hair Cells
Auditory Nerve
Place Theory
Frequency Theory
Volley Principle
Conduction Deafness
Nerve Deafness
I.
II.
III.
Sound: Sensing Waves of Vibrations
A.
Energy that travels in waves (vibrations)
B.
Must have a medium in order to exist
C.
Characteristics
1.
Amplitude (loudness)—the height of a wave
2.
Frequency—number of complete waves, or cycles, per second
3.
Travels much more slowly than light
4.
Measured in decibels (dB), an indication of perceived loudness
5.
Perception of pitch is related to wave frequency
The Ear: A Sound Machine
A.
Sound waves are captured and converted to neural form
B.
Ear components
1.
Eardrum—membrane that vibrates in response to sound waves
2.
Ossicles—three tiny bones in middle ear
a.
Hammer (malleus)
b.
Anvil (incus)
c.
Stirrup (stapes)
3.
Oval window—membrane connecting to inner ear
4.
Cochlea—fluid-filled snail-shaped bony tube
5.
Basilar membrane—vibrates within the cochlea
6.
Organ of Corti—gelatinous structure lined with hair cells
7.
Hair cells—auditory receptors
8.
Auditory nerve—transmits auditory messages to brain
C.
Location of sound determined by disparity between two ears’ messages
Perception of Pitch: Perceiving the Highs and Lows
A.
Place theory
1.
Developed by Hermann von Helmholtz
2.
Perceived sound related to vibration location on basilar membrane
3.
High frequencies—vibration near oval window
4.
Low frequencies—further down basilar membrane
B.
Frequency theory
1.
May best account for perception of lowest-frequency sounds
2.
Basilar membrane vibrates at same frequency as sound wave
IV.
C.
Volley principle—helps explain how mid-range sounds are detected
Hearing Loss
A.
Conduction deafness
1.
Damage to middle ear—eardrum or ossicles
2.
Hearing aids may help this problem
B.
Nerve deafness—damage to hair cells or to auditory nerve
C.
For protection avoid excessive noise, wear earplugs
MODULE 3.4 OUR OTHER SENSES: CHEMICAL, SKIN, AND BODY SENSES
After you have mastered the information in this unit, you will be able to:
 Explain how odors and tastes are sensed
 Discuss the skin senses
 Describe the kinesthetic and vestibular senses
Key Terms and Concepts:
Olfaction
Olfactory Nerve
Olfactory Bulb
Pheromones
Taste Cells
Taste Buds
Skin Senses
Gate-Control Theory of Pain
Acupuncture
Kinesthesis
Vestibular Sense
Semicircular Canals
Vestibular Sacs
I.
II.
III.
IV.
Olfaction: What Your Nose Knows
A.
Chemicals in the air that the nose can respond to
B.
Lock-and-key fitting of molecules into odor receptors
C.
Olfactory nerve—transmits odor information to brain
D.
Olfactory bulb—brain destination; odor information does not travel through thalamus
E.
Pheromones—chemical substances that play a role in behavior
Taste: The Flavorful Sense
A.
Four basic tastes: sweet, sour, salty, and bitter
B.
Flavors are a result of combinations of tastes
C.
Taste cells—taste receptors
D.
Taste buds—pores or openings on tongue (and surrounding area)
E.
Taste sensitivity partly genetic
F.
Supertasters—very dense network of tastebuds
The Skin Senses: Your Largest Sensory Organ
A.
Code information regarding touch, pressure, warmth, cold, and pain
B.
Sensory receptors distributed throughout body
C.
Somatosensory cortex—brain region processing skin sense information
D.
Specific receptors for warmth and cold
E.
Gate-control theory of pain—pain messages may be regulated via a neural gateway
F.
Acupucture may release endorphins—natural painkillers
The Kinesthetic and Vestibular Senses: Of Grace and Balance
A.
Kinesthesis tells us about body position and body movement
B.
Vestibular sense monitors body position in space
1.
Aids in keeping one’s balance
2.
Informs whether we are moving quickly, slowly
3.
The ear’s semicircular canals—movement of fluid relates body position information
4.
Dizziness: semicircular canal fluid still moving though we have stopped
MODULE 3.5 PERCEIVING OUR WORLD: PRINCIPLES OF PERCEPTION
After you have mastered the information in this unit, you will be able to:
 Define perception
 Discuss how perception is influenced by attention and perceptual set
 Describe the two general modes of processing visual stimuli
 Discuss the Gestalt principles of perceptual organization
 Define perceptual constancy and discuss the cues we use to perceive depth and motion
 Describe visual illusions
 Discuss the possible existence of subliminal perception Discuss the various forms of ESP and what
evidence, if any, supports its existence
Key Terms and Concepts:
Perception
Selective Attention
Habituation
Perceptual Set
Bottom-Up Processing
Top-Down Processing
Laws of Perceptual Organization
Proximity
Similarity
Continuity
Closure
Connectedness
Perceptual Constancy
Shape Constancy
Size Constancy
Color Constancy
Brightness Constancy
Binocular Cues
Retinal Disparity
Convergence
Monocular Cues
Visual Illusions
Stroboscopic Movement
Carpentered-World Hypothesis
Subliminal Perception
Extrasensory Perception
Parapsychology
Telepathy
Clairvoyance
Precognition
Psychokinesis
Ganzfeld Procedure
I.
II.
III.
IV.
V.
Perception—the Brain Organizes and Interprets Sensations
Attention: Did You Notice That?
A.
Attention—the first step in perception
B.
Selective attention—limit attention to certain stimuli
C.
Habituation—results from exposure to a constant stimulus
Perceptual Set: Seeing What You Expect to See
A.
Ambiguous stimuli interpreted differently based on expectations and preconceptions
Modes of Visual Processing
A.
Bottom-up processing—begin with specific features of shapes in environment
B.
Top-down processing—begin with knowledge and experience about patterns
Gestalt Principles of Perceptual Organization
VI.
VII.
VIII.
IX.
X.
XI.
A.
Figure and ground—figures have shapes; ground does not
B.
Gestalt laws of grouping: proximity, similarity, continuity, closure, connectedness
Perceptual Constancies
A.
Shape constancy—shape seen as the same across various perspectives
B.
Size constancy—size perceived as same regardless of distance from perceiver
C.
Color constancy—color perceived the same despite changes in lighting
D.
Brightness constancy—brightness seen as the same though illumination may change
Cues to Depth Perception
A.
Binocular cues—need both eyes
1.
Retinal disparity—slightly differing image relayed to brain from each eye
2.
Convergence—based on degree of muscular tension needed to focus on an object
B.
Monocular cues—one eye sufficient
1.
Relative size: larger objects perceived as closer
2.
Interposition: obscured object perceived as farther away
3.
Relative clarity: distant objects are blurrier
4.
Texture gradient: closer objects appear coarser
5.
Linear perspective: parallel lines appear to converge in distance
6.
Shadowing: light and dark are cues to projections and indentations
Motion Perception
A.
Projected image of object moves across retina
B.
Changing size of object
Visual Illusions: Do Your Eyes Deceive You?
A.
Perceptual cues may lead to misinterpretation
B.
Stroboscopic movement—apparent movement
Cultural Differences in Perceiving Visual Illusions
A.
Experience plays a role in visual perception
B.
Carpentered-world hypothesis—an environment dominated by straight lines and angles
Exploring Psychology: Controversies in Perception
A.
Subliminal perception
1.
Perception of stimuli below the level of conscious awareness
2.
Two-thirds of Americans believe subliminal suggestions do work
3.
Does seem to occur in some cases; influence is subtle
B.
Extrasensory perception
1.
Perception that occurs without benefit of the known senses
2.
A major focus of study in parapsychology
a.
Telepathy—the ability to exchange thoughts without use of the senses
b.
Clairvoyance—the perception of events that are not available to the senses
c.
Precognition—the ability to foretell the future
d.
Psychokinesis—the ability to move objects without touching them
e.
Ganzfeld procedure—way of testing for ESP
3.
As yet no reliable, replicable findings of ESP that have withstood scientific scrutiny
MODULE 3.6 APPLICATION: PSYCHOLOGY AND PAIN MANAGEMENT
 Describe what psychologists have learned about controlling pain.
I.
II.
Gaining Control Over Pain
A.
Pain does protect us from danger
B.
Endorphins produced by body can help diminish experience of pain
Pain management strategies
A.
Distraction—directing attention away from pain
B.
Bottleneck pain at neurological gate—rubbing, heat and cold may block gateway
C.
Do something enjoyable—priming positive emotions reduces pain intensity
D.
Changing thoughts and attitudes—remain positive, focus on what can help
E.
Obtaining accurate information—about pain source and treatment
F.
Meditation—focused attention yields a relaxed, contemplative state
G.
Biofeedback training—learning to control tension and other responses by the body