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Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Sensation and Perception
Chapter 3
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Sensation vs. Perception
SensationThe experience of sensory stimulation
PerceptionThe process of creating meaningful patterns
from raw sensory information
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Nature of Sensation
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Basic Process
Receptor cellsSpecialized cells that respond to a particular
type of energyDoctrine of specific nerve energies
One-to-one relationship between stimulation of a specific nerve and the resulting sensory experience
For example, applying pressure with your finger to your eye results in a visual experience
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Sensory Thresholds
Absolute thresholdThe minimum amount of energy that can be
detected 50% of the time
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Absolute Thresholds
Taste: 1 gram (.0356 ounce) of table salt in 500 liters (529 quarts) of water
Smell: 1 drop of perfume diffused throughout a three-room apartment
Touch: the wing of a bee falling on your cheek from a height of 1cm (.39 inch)
Hearing: the tick of a watch from 6 meters (20 feet) in very quiet conditions
Vision: a candle flame seen from 50km (30 miles) on a clear, dark night
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Sensory Thresholds
Sensory adaptationAn adjustment of the senses to the level of
stimulation they are receiving Difference threshold
The smallest change in stimulation that can be detected 50% of the time
Also called the just noticeable difference
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Sensory Thresholds
Weber’s LawStates that the difference threshold is a
constant proportion of the specific stimulusSenses vary in their sensitivity to changes in
stimulation
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Subliminal Perception
The notion that we may respond to stimuli that are below our level of awareness
Research shows that the effect only occurs in controlled laboratory studies
Research outside the laboratory shows no significant effect of subliminal information
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Extrasensory Perception
Refers to extraordinary perception such asClairvoyance – awareness of an unknown
object or eventTelepathy – knowledge of someone else’s
thoughts or feelingsPrecognition – foreknowledge of future events
Research has been unable to conclusively demonstrate the existence of ESP
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Vision
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Visual System
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
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Visual System
Lens Focuses light onto the
retina Retina
Lining of the eye containing receptor cells that are sensitive to light
Fovea Center of the visual
field
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Receptor Cells
Cells in the retina that are sensitive to lightVisual receptors are called rods and cones
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Receptor Cells
RodsAbout 120 million rodsRespond to light and darkVery sensitive to lightProvide our night vision
ConesAbout 8 million conesRespond to color as well as light and darkWork best in bright lightFound mainly in the fovea
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Receptor Cells
Bipolar cells Receive input from
receptor cells Ganglion cells
Receive input from bipolar cells
Blind spot Area where axons of
ganglion cells leave the eye
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Adaptation
Dark adaptationIncreased sensitivity of rods and cones in
darknessLight adaptation
Decreased sensitivity of rods and cones in bright light
AfterimageSense experience that occurs after a visual
stimulus has been removed
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
From Eye to Brain
Optic nerve Made up of axons of
ganglion cells carries neural
messages from each eye to brain
Optic chiasm Point where part of
each optic nerve crosses to the other side of the brain
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Color Vision
Properties of colorHue – refers to colors such as red and greenSaturation – refers to the vividness of a hueBrightness – the nearness of a color to white
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Theories of Color Vision
Additive color mixingMixing of lights of different huesLights, T.V., computer monitors (RGB)
Subtractive color mixingMixing pigments, e.g., paints
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Theories of Color Vision
Trichromatic theoryThree different types of cones
RedGreenBlue-violet
Experience of color is the result of mixing of the signals from these receptors
Can account for some types of colorblindness
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Forms of Colorblindness
Approximately 10% of men and 1% of women have some form of colorblindness
Dichromats People who are blind to
either red-green or blue-yellow
Monochromats People who see no color at
all, only shades of light and dark
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Theories of Color Vision
Trichromatic theory cannot explain all aspects of color visionPeople with normal vision cannot see
“reddish-green” or “yellowish-blue”Color afterimages
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Theories of Color Vision
Opponent-process theoryThree pairs of color receptors
Yellow-blueRed-greenBlack-white
Members of each pair work in oppositionCan explain color afterimages
Both theories of color vision are valid
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Color Vision in Other Species
Other species see colors differently than humans
Most other mammals are dichromatsRodents tend to be monochromats, as are
owls who have only rodsBees can see ultraviolet light
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Hearing
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Sound
Sound waves Changes in pressure
caused by molecules of air moving
Frequency Number of cycles per
second in a wave, measured in Hertz (Hz)
Frequency determines pitch
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Sound
Amplitude Magnitude (height) of
sound wave Determines loudness,
measured in decibels (dB) Overtones
Multiples of the basic tone Timbre
Quality of texture of sound
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Ear
Eardrum Middle ear
Contains three small bones; the hammer, anvil, and stirrup
These bones relay and amplify the incoming sound waves
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Ear
Oval window Membrane between
middle ear and inner ear
Cochlea Part of inner ear
containing fluid that vibrates
This causes the basilar membrane to vibrate
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Ear
Basilar membrane Membrane in the
cochlea which contains receptor cells, called hair cells
Auditory nerve Connection from ear to
brain Provides information
to both sides of brain
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Theories of Hearing
Place theoryPitch is determined by location of vibration
along the basilar membraneFrequency theory
Pitch is determined by frequency hair cells produce action potentials
Volley PrinciplePattern of sequential firing determines pitch
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Hearing Disorders
About 28 million people have some form of hearing damage in the U.S.
Can be caused byInjuryInfectionsExplosionsLong-term exposure to loud noises
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Other Senses
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Smell
Detecting common odors Odorant binding protein is
released and attached to incoming molecules
These molecules then activate receptors in the olfactory epithelium
Axons from those receptors project directly to the olfactory bulb
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Smell
Women have a better sense of smell than men
AnosmiaComplete loss of the ability to smell
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Smell
Pheromones Used by animals as a form of communication Provides information about identity Also provides information about sexual receptivity
Pheromones stimulate the vomeronasal organ (VNO)
Information from the VNO is sent to a special part of the olfactory bulb used for pheromonal communication
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Taste
Four basic tastesSweetSaltySourBitter
Recent discovery of fifth tasteUmami
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Taste
Receptor cells are located in taste buds
Taste buds are located in papillae on the tongue
Chemicals dissolve in saliva and activate receptors
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Other Senses
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Kinesthetic Senses
Kinesthetic senses provide information about speed and direction of movementStretch receptors sense muscle stretch and
contractionGolgi tendon organs sense movement of
tendons
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Vestibular Senses
Vestibular senses provide information about equilibrium and body position
Fluid moves in two vestibular sacsVestibular organs are also responsible for
motion sicknessMotion sickness may be caused by
discrepancies between visual information and vestibular sensation
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Skin Senses
Skin is the largest sense organThere are receptors for pressure,
temperature, and painTouch appears to be important not just as
a source of information, but as a way to bond with others
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Pain
Serves as a warning about injury or other problem
Large individual differences in pain perception
Gate control theoryNeurological “gate” in spinal cord which
controls transmission of pain to brain
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Pain
Biopsychosocial theory Holds that pain involves not just physical stimulus, but
psychological and social factors as well Placebo effect
Shows that when a person believes a medication reduces pain, their pain is often reduced even though no medication was given
Pain relief is likely the result of endorphin release
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Pain
Alternative approachesHypnosisSelf-hypnosisAccupuncture
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Perception
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Perceptual Organization
Figure-ground We perceive a
foreground object (figure) against a background (ground)
Animals may look like the background they inhabit as a way of destroying figure-ground distinction
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Perceptual Organization
Other principles of organization Proximity Similarity Closure Continuity
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Perceptual Organization
Perceptual Constancy Our tendency to
perceive objects as stable and unchanging despite changing sensory information
Size constancy Shape constancy Brightness constancy Color constancy
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Perception of Distance and Depth
Monocular cues – those that require only one eye Aerial perspective Texture gradient Linear perspective Motion parallax Superposition
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Perception of Distance and Depth
Binocular cues – those that require both eyesRetinal disparityConvergence
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Localizing Sounds
We use both monaural and binaural cues
Loudness Louder sounds are
perceived as being closer Time of arrival
Sounds will arrive at one ear sooner than the other
This helps determine direction of the sound
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Perception of Movement
Apparent movementIllusion that still objects are moving
Autokinetic illusionPerceived motion of a single object
Stroboscopic motionCreated by a rapid series of still pictures
Phi phenomenonApparent motion created by lights flashing in
sequence
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Visual Illusions
Occur because of misleading cues in the stimulus
Gives rise to false perceptions
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Individual Differences and Culture in Perception
MotivationOur desires or needs shape our current
perceptionsValuesExpectationsCognitive StyleExperience and CulturePersonality