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Transcript of + Chapter 5 Sensation James A. McCubbin, PhD Clemson University Worth Publishers.
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Chapter 5
Sensation
James A. McCubbin, PhDClemson University
Worth Publishers
Sensation
Sensation a process by which our sensory
receptors and nervous system receive and represent stimulus energy
Perception a process of organizing and
interpreting sensory information, enabling us to recognize meaningful objects and events
Sensation and Perception
Paris
in the the spring
Sensation and Perception
Sense Input PerceptionSight colors/shapes object/
eventHearing sound/noise words/musicTouch pressure/temp feel of objectTaste sour/salty/bitter/sweet flavorSmell spicy/resinous/burned odor rotten/fruity/flowery
Perception
Physiological variables: Receptors available Receptor limits Receptor abnormalities Sensory adaptation- diminished
sensitivity as a consequence of constant stimulation
Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Put a band aid on your arm and after awhileyou don’t sense it.
Perception
Psychological variables Interests Motivation Expectancy set Emotion Attitudes Values
Gestaltists
Gestalt means “whole” in German. The Gestaltists believed that people look to form patterns and complete whole images when they perceive things around them
Sensation and Perception
Sensation Our
sensory and perceptual processes work together to help us sort out complex processes
Sensation and Perception
Perceptually Impaired
Iti soft ennotre alized howcom plexT heproces sofrea ding is. Afe w sim plerear rang mentscan ha veyoucomp lete lycon f used!
Top-Down Processing
Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience
and expectations.
THE CHT
Bottom-up Processing
Analysis of the stimulus begins with the sense receptors and works up to the level of
the brain and mind.
Letter “A” is really a black blotch broken down into features by the brain that we perceive as an
“A.”
Sensation- Basic Principles
Psychophysics study of the relationship between
physical characteristics of stimuli and our psychological experience of them
Light- brightness Sound- volume Pressure- weight Taste- sweetness
Sensation- Thresholds
Absolute Threshold minimum stimulation needed to detect
a particular stimulus 50% of the time Difference Threshold
minimum difference between two stimuli required for detection 50% of the time
just noticeable difference (JND)
Sensation- Thresholds Signal Detection Theory
predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)
assumes that there is no single absolute threshold
detection depends partly on person’s experience expectations motivation level of fatigue
Sensation- Thresholds
Subliminal When stimuli
are below one’s absolute threshold for conscious awareness
0
25
50
75
100
Low Absolutethreshold
Medium
Intensity of stimulus
Percentageof correctdetections
Subliminal stimuli
Sensation- Thresholds
Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage light intensity- 8% weight- 2% tone frequency- 0.3% Ex. A three way bulb
Weber’s Law
Vision
Vision
Pupil- adjustable opening in the center of the eye
Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening
Lens- transparent structure behind pupil that changes shape to focus images on the retina
Retina’s Reaction to Light
Optic nerve- nerve that carries neural impulses from the eye to the brain
Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there
Fovea- central point in the retina, around which the eye’s cones cluster
Blind Spot
Vision- Stabilized Images on the Retina
Vision
Transduction conversion of one form of energy
to another in sensation, transforming of
stimulus energies into neural impulses
Wavelength the distance from the peak of one
wave to the peak of the next
Vision
Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina
Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information
Vision
Acuity- the sharpness of vision Nearsightedness- condition in which
nearby objects are seen more clearly than distant objects because distant objects in front of retina
Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina
Vision
Farsighted Nearsighted Normal Vision Vision
Vision
Vision
Hue dimension of color determined by
wavelength of light Intensity
amount of energy in a wave determined by amplitude brightness loudness
The spectrum of electromagnetic energy
Vision- Physical Properties of Waves
Short wavelength=high frequency(bluish colors, high-pitched sounds)
Long wavelength=low frequency(reddish colors, low-pitched sounds)
Great amplitude(bright colors, loud sounds)
Small amplitude(dull colors, soft sounds)
Retina’s Reaction to Light- Receptors
Rods peripheral retina detect black, white and gray twilight or low light
Cones near center of retina fine detail and color vision daylight or well-lit conditions
Photoreceptors
E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969
Color-Deficient Vision
People who suffer red-green blindness have trouble perceiving the number within the design
Visual Information Processing
Trichromatic (three color) Theory Young and Helmholtz three different retinal color receptors
red green blue
Afterimages
Opponent Process- Afterimage Effect
Visual Information Processing
Opponent-Process Theory- opposing retinal processes enable color vision“ON” “OFF”red greengreen red blue yellow yellow blue black whitewhite black
Pathways from the Eyes to the Visual Cortex
Visual Information Processing
Color Constancy Perceiving familiar objects as
having consistent color, even if changing illumination alters the wavelengths reflected by the object
Feature Detection
Nerve cells in the visual cortex respond to specific features, such as edges, angles,
and movement.
Ros
s K
inna
ird/
Alls
port
/ Get
ty I
mag
es
How the Brain Perceives
Illusory Contours
Visual Information Processing
Parallel Processing simultaneous processing of several
aspects of a problem simultaneously
The Ear
Dr. Fred H
ossler/ Visuals U
nlimited
The Ear
Pinna- the external funnel shaped portion of the ear
External Auditory Canal -directs sound waves to the eardrum
Eardrum- thin piece of skin that vibrates to incoming sound
Audition- The Ear
Middle Ear chamber between eardrum and cochlea
containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window
Inner Ear innermost part of the ear, contining the
cochlea, semicircular canals, and vestibular sacs
Cochlea coiled, bony, fluid-filled tube in the inner ear
through which contains the cilia receptors for hearing on the basilar membrane.
Audition
Audition the sense of hearing
Frequency the number of complete
wavelengths that pass a point in a given time
Pitch (measured in Hertz) a tone’s highness or lowness depends on frequency
Audition
Place Theory the theory that links the pitch we hear
with the place where the cochlea’s membrane is stimulated
Frequency Theory the theory that the rate of nerve
impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch
How We Locate Sounds
Location with Sound
Doppler Shift- as something approaches the pitch is higher and as it recedes the pitch is lower. Ex. The train coming into the station.
The Intensity of Some Common Sounds
Audition Older people tend to hear low frequencies well
but suffer hearing loss for high frequencies
1time
10times
100times
1000times
32 64 128 256 512 1024 2048 4096 8192 16384
Frequency of tone in waves per second
Low Pitch High
Amplitude required forperception relative to 20-29 year-old group
Deafness
Tinnitus- ringing in the ears when there is no external auditory stimulation caused by exposure to loud noise and represents damage to the auditory nerve.
Deafness
Conduction Hearing Loss hearing loss caused by damage to the
mechanical system that conducts sound waves to the cochlea
Nerve Hearing Loss hearing loss caused by damage to the
cochlea’s receptor cells or to the auditory nerve
Deafness
Choices in adjusting to hearing loss:Lip reading- family members and others
must be careful to insure that their lips can be seen at all times during conversation
American Sign Language- a set of symbols that represent words or phrases
Cochlear Implant- an electrode is placed in the cochlea that artificially sends sound to the temporal lobe.
Touch
Skin Sensations pressure
only skin sensation with identifiable receptors most on the hands and back of neck EX back vs. face 2pt. threshold
warmth cold pain
Touch
The sense of touch is a mix of four distinct skin senses—pressure, warmth, cold, and pain.
Bru
ce A
yers
/ Sto
ne/ G
etty
Im
ages
Skin Senses
Only pressure has identifiable receptors. All other skin sensations are variations of
pressure, warmth, cold and pain.
Burning hot
Pressure Vibration Vibration
Cold, warmth and pain
Pain
Pain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues. A rare disease exists in
which the afflicted person feels no pain.
Ashley Blocker (right) feels neither painnor extreme hot or cold.
AP Photo/ Stephen M
orton
Biopsychosocial Influences
Gate-Control Theory
Melzack and Wall (1965, 1983) proposed that our spinal cord contains neurological “gates” that either block pain or allow it to be sensed.
Gary C
omer/ PhototakeU
SA.com
Pain Gate-Control Theory
theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain
“gate” opened by the activity of pain signals traveling up small nerve fibers
“gate” closed by activity in larger fibers or by information coming from the brain
Pain
State of mind can affect intensity of pain:
WWI soldiers were relieved to be wounded to escape the terror of the battlefield.
Athletes “play with pain” due to endorphins and realize the next day how they have injured themselves.
Pain tolerance
Touch
There seems to a biological need for touch.Babies who are not touched suffer from
“failure to thrive” which means they do not grow and eventually die.
Premature babies in a study by Tiffany Field wear proven to benefit from daily massage and went home from the hospital sooner.
In adults massage lowers cortisol levels and reduces the effect of stress.
People in this culture have been “touch starved”.
Body Position and Movement
Kinesthesis the system for sensing the position and
movement of individual body parts Proprioception-sense of the movement
of muscles and tendons (body parts) in space.
Vestibular Sense the sense of body movement and
position including the sense of balance
Taste
Traditionally, taste sensations consisted of sweet, salty, sour, and bitter tastes. Recently, receptors
for a fifth taste have been discovered called “Umami”.
Sweet Sour Salty Bitter Umami(Fresh
Chicken)
Taste
Taste Receptors
Taste Taste Sensations
sweet sour salty Bitter
Some taste sensations are genetically programmed, such as sweet, and finding bitter and sour foods unpleasant
A study of babies had sweet eliciting smiles, lip smacking, and sour eliciting protrusion of tongue
These reactions make good evolutionary sense Animals tend to be neophobic, and human children are
reluctant to try new things One experiment asked a group of subjects to taste two
groups of food (that were the same). When the items were accurately named (chopped tomatoes, oatmeal, beefsteak) more willing them when given novel names (pendula fruit, lat, langua steak)
Taste
Moisture is necessary for taste buds to function.
Taste buds are located in the fungiform papillae or bumps on the tongue. There are many taste buds in each bump.
Supertasters have an extraordinary number of taste buds and fungiform papillae. They can always taste PROP.
Spicy food tastes very hot to supertasters as the taste bud are linked to pain receptors that respond to the hot oil.
Taste
Sensory interaction- taste is highly dependent on smell. The two together create flavor. This is evident when you have a cold. Taste also depends on sight. If it doesn’t look good, it doesn’t taste good.
Chocolate increases serotonin particularly in women and increases happiness.
Smell
Receptor cells inolfactory membrane
Nasal passage
Olfactorybulb
Olfactorynerve
SmellLike taste, smell is a chemical sense.
Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. Unlike taste,
there are many different forms of smell.
Age, Sex and Sense of Smell
Women
Men
10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99Age Group
4
3
2
0
Numberof correct
answers
Women and young adults have best sense of smell
Smell
Theories of smell:Lock and Key- odor molecules fit
specific receptor sitesReceptor construction- as a molecule
enters the system an appropriate receptor is formed.
Smell
Olfactory cells are located on the cilia in the upper portion of the nose. They are surrounded by mucus to trap odor molecules.
Smell is associated with memory encoding.
Smell declines with ageAnosmia- 2 million people have no sense
of smell. Can be the result of head trauma or infection or cold.
Smell
Pheromones-sexual signals through smell. Used by animals and maybe humans. Ex. Sweaty t-shirts, menstrual synchrony
Smell is important to taste. Ex. When one has a cold.