PSYCHOLOGY: Chapter 8  Sensation and Perception Lecture Notes

How do we "feel" a sensation?: physical change in the external or internal environment triggers chemical, electrical, and mechanical activity in the sense receptors.  After complex processing in the central nervous system, a pattern of activity is produced in certain areas of the brain.  This creates the sensation.

Sensation:  when a stimulus activates receptor cells.

Perception:  the organization of sensory information into meaningful experience. (The chemical process taking place in the brain is sorted and sent out.)

     * No one perceives in exactly the same way.

Environmental psychologists: focus on the relationships between people and their physical and social surroundings.

Stimulus: any aspect or change in environment to which an organism responds.

4 methods of measuring stimuli:

- size

- wavelength

- duration

- intensity.

Difference between stimulus and sensory experience: a stimulus causes (it precedes) the sensory experience. (it follows the stimulus) the effect

Psychophysics: the study of the relationships between sensory experiences and the physical stimuli that cause them.

        - Goal of: to develop a measurable relationship between stimuli from the world (such as frequency and intensity) and sensory experiences (such as

                          pitch and loudness) that produced by them.

Absolute threshold: the minimum amount of physical energy required to produce a sensation at least 50% of the time. 

                                 (At what point does someone respond to it.)

The Human Senses/Sensations Chart

Sensory Differences and Ratios

Another type of threshold is the difference threshold - the smallest change in a  physical stimulus that can be detected between two stimuli.

A related concept is the just noticeable difference, or JND.

     - Just Noticeable Difference:  the smallest increase or decrease in the intensity of a stimulus that a person is able to detect.

Sensory deprivation: occurs whenever a person is denied the use of one or more senses - very low absolute threshold

 Threshold levels of senses: Sense receptor cells have extremely low absolute thresholds.

Difference threshold: the minimum amount of a change in physical energy needed to produce a change in the sensation.

Effect of change in stimulus: Psychologists have found that a particular sensory experience depends more on changes in the stimulus than on the absolute

                                                 size or amount of the stimulus.

Weber's Law: the principle that the larger or stronger the stimulus, the larger the change required for an observer to notice a difference.

        - The change must be proportional.

        - See the Back pack example page 111

Phantom Limb Pain: someone who has had an amputation but still "feels" some sensations coming from the missing part.  What happens is that one's brain

                                receives the nervous impulses coming up a certain ascending tract, which it associates with that limb.

        - 5 Reactions to amputation: tingling, warmth, coldness, pain, and/or heaviness.

        - % Who experiences it: 1/3 of the amputees will experience it.

        - Duration: it can last for a year or forever.

     -3 possible causes:

* abnormal sympathetic nervous system activity

* irritation of the stump

* emotional disturbance 

Sensory Adaptation: the ability of the senses to adjust to a new level of stimulus and respond only to changes away from that level.

- 3 things senses are most responsive to: increases, decreases, or new events

Examples: When you go to the movies during the day, when you go outside and your eyes have to adjust to the light.  Or in swimming, the

                  water only feels cold in the beginning, then your skin receptors have adjusted to the temperature.

        - without sensory adaptation: you would feel the constant pressure of the weight of your clothes.

- Physiological nystagmus: series of tremors of the eye; a constant series of preventing receptor cells from adapting.

Effect of motivation on perception: The individual has to make a decision on subconscious level to pay attention to it.

3 things that affect perception: an individual's feelings, expectations, and motivations

Signal-detection theory: a summary of mathematical relationships between motivation, sensitivity, and sensation.

        - Detection thresholds: recognizing some stimulus against a background of noise.

                * Example: An air traffic controller reading the "blips" on the radar.  They have to know which signals are planes, and which are visual noise

                                  (more commonly known as ground clutter).

Psychologists have identified two different types of processing stimuli, or signals.

                1.) Preattentive process is a method for extracting information automatically and simultaneously when presented with stimuli.

                2.) Attentive process is a procedure that considers only one part of the stimuli presented at a time.

5 senses: hearing, smell, vision, touch, and taste

4 skin senses: pressure, warmth, coldness, and pain

2 internal "senses": vestibular and kinesthetic

Types of stimului for sensory receptors: light, chemical molecules, sound waves, pressure, pain, pressure and texture.

Vision: the most studied of all senses.  It gives us a great deal of information about our environment and the objects in it – the sizes, shapes, and

           locations of things, and their textures, colors, and distances.

        - How it occurs: Light enters through the pupil and reaches the lens, (a flexible structure that focuses light on the retina). 

                                  The retina contains two types of light-sensitive  receptor cells: the rods and cones.

                                  These change light energy into neural impulses, which then travel over the optic nerve to the brain.

        - Parts of the eye:  (see handout)

                * Cornea: focuses light into the eye

                * Iris: colored part focuses the light

                * Pupil: the center of eye, determines how much light is let into the eye

* Lens: clear, flexible structure that focuses light rays onto retina

* Retina: connects to the optic nerve, lines the back of the eye, it senses light

                * Macula: small area contains special light sensitive cells; it allows us to see fine details.

                        ** As we age get a small degree of macular degeneration.  This is why most people over the age of 40 begin to need bifocal glasses

                             to read.

                * Vitreous: clear, jelly substance fills the middle of the eye

        - Rods: receptor cells in the retina that are sensitive to light, but not to color.  These are helpful in night vision.

 * # of: 75-150 million per eye.

        - Cones: receptor cells in the retina that are sensitive to color.  These are useful in daytime vision.

        * # of: 6-7million per eye.

- Optic nerve- the nerve that carries impulses from the eye to the brain

- Color deficiency: (More commonly called color blindness) A genetic abnormality in which all or part of a person’s cones do not function properly. 

                               Some do see some color.

                * 3 types: red/green, yellow/blue, and total.               

^ Total color blindness: 2 major types

                                ~ Typical: can't discriminate between colors

                                ~ Atypical: can see some color but mostly onlybright colors.

                * % affected: 8% of men, and  1% of women

                * Cause: It is a genetic defect in the cones.  The defect is carried in the genes of women whose vision is usually normal.  The women pass these

                              genes on to their sons, who are born color-deficient.

3 optic diseases:  Glaucoma, Cataracts, and Color deficiency

- Glaucoma: condition in which the optic nerve is damaged.  It damages the nerve fibers which  cause blind spots to develop. Pressure

                    (called intraocular pressure) builds up in the eye when the clear fluid (called aqueous humor), which normally flows in and out of the eye,

                    is prevented from draining properly.  The resulting pressure within the eye can damage the optic nerve.

     * There are 5 types of glaucoma

        * Symptoms: None

        * Treatment: medication or surgery

- Cataracts: These are a cloudy or opaque area in the normally transparent lens of the eye.   As this area thickens, it prevents light rays from

                     passing through the lens and focusing on the retina.  They can take from a few months to several years to develop.

* Cause: by the natural aging process, injury, chronic eye disease, or diabetes.

* Symptoms: blurred vision; sensitivity to light and glare; increased near-sightedness; or seeing distorted images.

* Treatment: Surgery to remove the diseased lens.  The removed lens is replaced by glasses or a special type of contact lens, called an

                      intraocular lens implant.

* More than half the people over age 65 have some degree of cataract development.

        - Color deficiency: when some or all of a person's cones do not function properly  (See above)

Binocular fusion: the process of combining the images received from the two eyes into a single fused image.

Retinal disparity: the differences between the images stimulating each eye.

Stereopsis: the use by the visual system of retinal disparity to give depth perception - providing a three-dimensional appearance to the world.

Hearing: depends on vibrations of the air called sound waves.

- How we hear: sound waves from air pass through bones and fluids until they reach the inner ear. In the inner ear there are hair like receptor

                          cells, which move back and forth to capture the sound wave. Which change sound vibration into a nerve impulse that travel up

                          auditory nerve to brain.

- Sound waves: vibrations in the air

- 3 bones: Malleus, incus, stapes

- Auditory nerve: carries impulses from ear to brain results in impulses of sound

- Decibel: measure of the physical intensity of sound, which is lawfully related to the sensation of loudness.

* 0: softest sound to human can hear

* 140: as loud as jet plane taking off.

* 150:  Most concerts run are at this level.

* Any sound over 110: can damage hearing.

* Persistence of damage level: Persistent sounds as low as 80 decibels can damage hearing.  This damage takes place over time, so it is

                                                  hard to notice any damage.

        ** Many people listen to their car stereos at a higher level than 80 decibels!

* # Of Americans regularly exposed to 110+ decibels at work: 10 million Americans.  This will result in permanent hearing damage.

- Pitch: the experience associated with a sound’s frequency; the “highness” or “lowness” of a sound.

        * Low frequencies: produce deep bass sounds.

     * High frequencies: produce shrill squeaks

10 causes of hearing loss:

        Blockage of the outer ear

        Genetic predisposition

        Exposure to loud noise

        Deterioration from aging

        Trauma (such as a head injury or brain tumor)

        High fever

        Malfunction of the middle ear (disruption of the bones or eardrum)

        Buildup of fluid in the middle ear

        Infection that reaches the inner ear

        Damage to the nervous system.

- 2 major causes: aging and exposure to loud noise.

4 types of hearing loss (See Hearing Loss Handout)

1.) Conductive: sound is not conducted efficiently through the outer and/or middle ear, causing speech and other sounds to be heard less clearly

                          or sound muffled.  (The temporary hearing loss due to sound not getting through.)  Caused by infection, wax build up, colds/allergies,

                          or ruptured ear drum.

                * This kind of hearing loss can often be medically or surgically corrected.

2.) Sensorineural: loss is (99% permanent) caused by damage in the inner ear or nerve pathways to the brain.  Certain sounds are heard less

                             distinctly than others, causing distortion and reduced understanding of speech.

*While this kind of hearing loss is usually not medically correctable, people with sensorineural hearing loss can often be helped by

  using a hearing aid or other amplification device.

3.) Mixed: A combination of the above.

4.) Noise-induced: can be caused by a one-time exposure to loud sound as well as by repeated exposure to sounds at various loudness levels over

                               an extended period of time. The loudness of sound is measured in units called decibels. 

How injured:  Exposure to harmful sounds causes damage to the sensitive hair cells of the inner ear and to the nerve of hearing. These structures can be

                       injured by noise in two different ways: from an intense brief impulse, such as an explosion or from continuous exposure to noise, such as

                       that in a woodworking shop.

                       The effect from impulse sound can be instantaneous and can result in an immediate hearing loss that may be permanent.  The structures of

                        the inner ear may be severely damaged.  This kind of hearing loss may be accompanied by tinnitus, an experience of sound like ringing,

                        buzzing or roaring in the ears or head, which may subside over time.

                        The damage that occurs slowly over years of continuous exposure to loud noise is accompanied by various changes in the structure of the

                        hair cells. It also results in hearing loss and tinnitus. Exposure to impulse and continuous noise may cause only a temporary hearing loss.

                        If the hearing recovers, the temporary hearing loss is called a temporary threshold shift, and largely disappears within 16 hours after

                        exposure to loud noise.

          Both forms of NIHL can be prevented by the regular use of hearing protectors such as earplugs or ear muffs.

Presbycusis: the loss of hearing that occurs in most individuals as they grow older.

The loss associated with presbycusis is usually greater for high-pitched sounds. For example, it may be difficult for someone to hear the nearby chirping of a bird or the ringing of a telephone.

However, the same person may be able to hear clearly the low-pitched sound of a truck rumbling down the street.   Presbycusis most often occurs in both ears, affecting them equally. Because the process of loss is gradual, people who have presbycusis may not realize that their hearing is diminishing. The loss may be mild, moderate, or severe.

                        ^ Symptoms of presbycusis

                               ~ With presbycusis, sounds often seem less clear and lower in volume. This contributes to difficulty hearing and understanding speech.

                               ~ The speech of others seems mumbled or slurred.

                               ~ High-pitched sounds such as "s" and "th" are difficult to hear and tell apart.

                               ~ Conversations are difficult to understand, especially when there is background noise.

                               ~ A man's voice is easier to hear than the higher pitches of a woman's voice.

                               ~ Certain sounds seem annoying or overly loud.

                                ~ Tinnitus (a ringing, roaring, or hissing sound in one or both ears) may also occur.

                        ^ Causes of presbycusis: Sensorineural hearing loss is caused by disorders of the inner ear or auditory nerve.  Presbycusis is

                                                                 usually a sensorineural hearing disorder.  Sensorineural hearing loss is most often due to a loss of hair cells

                                                                 (sensory receptors in the inner ear).  It is most commonly caused by gradualchanges in the inner ear. 

                                        Other causes are:

        ~ as a result of hereditary factors as well

                                                        ~ aging

        ~ various health conditions

        ~ side effects of some medicines (aspirin and certain antibiotics).

        ~ the cumulative effects of repeated exposure to daily traffic sounds or construction work

        ~ noisy offices

                                                        ~ equipment that produces noise

                                                        ~ loud music

        ~ changes in the blood supply to the ear because of heart disease, high blood pressure, vascular (pertaining to blood

           vessels) conditions caused by diabetes, or other circulatory problems.

Symptoms related to hearing loss:

               * an increased need for loud volume on the T.V. or radio, straining to hear conversations, especially in group situations or with background noise

               * a ringing or buzzing in the ear(s)

               * a need to often ask a speaker to repeat himself/herself

               * favoring one ear over the other

               * a lack of response to nearby sounds when others respond.

               * words like "shore" and "four" or "son" and "fun" may sound the same to you.

 4 common treatments for hearing impairment:

                Medication: These are most effective in the case of conductive hearing loss. Antibiotics and other drugs can often help heal infections and

                                   control dizziness.

                Instruction: Instruction helps individuals to use their remaining hearing to its best advantage. Instruction may include aural rehabilitation,

                                   speech-reading, finger spelling, signing, etc.

                Surgery: Surgery may be effective in rebuilding the middle ear, removing infections, or relieving pressure. Surgery may also involve the implanting

                               of electrodes into the organ of hearing.

                Hearing Aids: Hearing aids are miniature electronic amplifiers that can increase and control sound intensity and expand the range of tones

                                      heard.  Recent advances in programmable and digital hearing aids have markedly improved their ability to compensate for many

                                      common hearing problems.

Audiologist:  a professional educated in the study of normal or impaired hearing. The audiologist determines if a person has a  hearing impairment, what

                     type of impairment it is, if a medical  referral is necessary, and how the individual can make the best use of remaining hearing.

Chemical senses: smell and taste.

- why are they called “chemical senses”?: their receptors are sensitive to chemical molecules  rather than to light energy or sound waves.

- Process of smell: The appropriate molecules must come into contact with the smell receptors in your nose.

                                The molecules enter your nose in vapors, which reach a special membrane in the upper part of the nasal passages on which

                                the smell receptors are located. 

                                These receptors send messages about smells via the olfactory nerve to the brain.

        * Total number of taste buds: 10,000 (on your tongue, palate, and cheeks)

        * Number of taste buds on the tongue: 9,000

        * Number of receptors on each taste bud: 50-150

- Olfactory nerve: nerve that carries smell impulses from the nose to the brain.

     * Total number of human olfactory receptor cells:  40 million  (Just for comparison, a rabbit has 100 million, and a dog has 1 billion.)

- Process of taste: For you to taste something, appropriate chemicals must stimulate receptors in the taste buds on your tongue. 

                                Taste information is relayed to the brain along with data about texture and temperature of the substance you have put

                                into your mouth.

4 primary sensory experiences of taste

     -sour

        -salty

        -bitter

        -sweet

- Beebe-Center, (1949): Scientists who did the original experiment that determined the four primary sensory experiences of taste.

The 6 Qualities of Smell

     -flowery

        -fruity

        -spicy

        -resinous

        -putrid

        -burned

     - Henning (1916): proposed that all smells are made up of the six qualities above.

        - Buck and Axel, 1991: Proposed the theory that there may be a thousand olfactory receptors, each responding only to a very limited number of

                                                gaseous molecules.

        *** Much of what is referred to as taste is actually produced by the sense of smell.

                Example: You have undoubtedly noticed that when your nose is blocked by a cold, foods usually taste bland.

4 sensations that affect taste

         - warmth

- cold

- pressure

- texture

Role of the chemical senses: They play a relatively unimportant role in human life when compared to their functions in lower animals.

        - in humans: smell and taste have become more a matter of esthetics than of survival.

     - in animals: They often depend on smell to communicate with one another, especially in mating.

4 stimuli for skin receptor cells:

            - pressure

- warmth

- cold

- pain

- areas of high receptor density: Fingertips are densely populated with receptors (2,700 per square centimeter) and are highly sensitive. 

                                                       (The hand has 17,000 receptors total)

- areas of low receptor density: Middle of your back, your heel, or the back of your calf.

Importance of pressure sensations: serve as a protective function.  It alerts us danger.

Effect temperature has on sensation: In order to create a hot or cold sensation, a stimulus must have a temperature greater of less than the temperature

                                                             of the skin.

Pain

Reasons for pain: alerts us to real or potential danger, allows us to prevent damage, it’s an emergency system that demands immediate action.

Pain: (Also See handout) 

The word pain derives from the Latin poena meaning punishment from the ancient belief that pain results from some kind of retribution.  The experience of pain, broadly speaking, is a product of chemical messengers, emotions and thoughts involving pain. Pain messages travel along the spinal cord to the brain. Chronic pain reaches the hypothalamus which instructs the pituitary gland to release certain stress hormones. This is where our emotions are processed which explains why our feelings can influence pain.

     *** Pain receptor cells do not go through sensory adaptation.

     - 3 types: referred, chronic, and acute pain

                * Referred: pain in area away from actual pain stimulus

           * Acute: immediate onset, short duration less than 2 months.

           * Chronic: pain on a "deeper" level which persists over 3 months: can be constant or intermittent.

        - Pain intensity can be mild, moderate, severe, intermediate or continous.

        - Pain Gate Theory: The pain gate theory was discovered in 1965 by Dr’s Melzack & Walls, it works on the theory that nerve gates in the spinal cord,

                                        open to allow pain through or close to block it’s passage. Medicines, acupuncture, deep muscle massage & many alternative treatments

                                        may be able to block the pain gates, thus lessening the pain.

                                        We know that A - delta fibres release substance ‘P’ which opens the gate, and A - beta fibres release Enkephalin which inhibits

                                        Substance ‘P’ and closes gate.

We do not truly understand pain from deep within the body.  Pain is a subjective experience.  Because pain is such a major part of life, hospitals are now using a "pain level" scale as one of the vital signs-like pulse rate or blood pressure- to access patient health.

Vestibular system: three semicircular canals located in the inner ear and connected to the brain by the vestibular nerve. It helps control balance.

     - Semicircular canals: make up Vestibular system; fluid in them has to stay at certain level to provide a sense of balance.

- 3 types of stimuli for vestibular response:

* spinning

* falling

* tilting

- 2 effects of over stimulation of the vestibular system: dizziness and motion sickness

Motion sickness: a condition that occurs when a person’s body is in motion and the inner ear becomes over stimulated or confused.  Makes you feel dizzy,

                           and nauseous.

- Ways to prevent motion sickness:

* position yourself where there is the least movement

* recline seat

* avoid large meals (eat small meals)

* take frequent small amounts of fluids and simple foods (Sprite and crackers)

* avoid reading,

* watch the ground some distance away from the vehicle

* watch horizon.

        - Effect on children: are especially prone to motion sickness  because they cannot see out of the car, so they lose visual contact with their environment. 

                                            Position the child so he/she can see.  (Animals will react like kids too.)

Kinesthesis: the sense of body movement and body position, acquired through the receptors located in and near the muscles, tendons, and joints.

                    It cooperates with the vestibular system and visual senses to maintain posture and balance.

        - 3 locations of receptor cells: in and near the muscles, tendons, and joints

- 4 stimuli internal receptor cells respond to:

- pressure

- temperature

- pain

- chemicals

Perception: the organization of sensory experience into meaningful wholes.

Gestalt: in perception, the experience that comes from organizing bits and pieces of information into meaningful wholes.