+ 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

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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

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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.

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How the Brain Perceives

Illusory Contours

Visual Information Processing

Parallel Processing simultaneous processing of several

aspects of a problem simultaneously

The Ear

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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.

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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.

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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.