PSYCHOLOGY: Chapter 8  Sensation and Perception Lecture Notes


8-1: Sensation


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


Subliminal advertising: attempt to influence people with messages that are below normal thresholds of detection.


Subliminal perception: the ability to notice stimuli that affect only the subconscious mind.


Anthony Greenwald (1990): psychologist who created a study in which they switched the labels on two subliminal tapes - one on memory and one on

            improving self-esteem.  At the end of one month, participants reported on improvement on whatever tape said on the label.  Obviously, some of the

            effect of subliminal material is the power of the mind.


Propaganda: (See handout in study guide)

     9 types


Name calling - using negative labels to discredit a competitor. Mudslinging in politics.


Bandwagon - appealing to people's desire to "go with the crowd"


Glittering generalities - broad statements appeal to emotions. Accepted trait- democracy, "family, values", American, Christian


Card stacking - slanting the facts.  Using statistics to "prove" your point.


Plain folks - using folksy language to appeal with common people


Transfer - connecting product with someone/something that’s admired - symbols, quotes, images, religion


Testimonial - famous people selling stuff.  Ex. Michael Jordan - Nike shoes, Jeff Gordon-Pepsi


Logical Fallacies - applying logic usually draw a conclusion from one or more established premise, premise may be true - conclusion may not be true


        Example- Syllogism

                P- Aristotle is a Greek

                P2- All Greeks are human.

                C- Therefore Aristotle is human. 


      As long as premises are correct conclusion should be correct, BUT it is not.


Fear - present dreaded circumstance, usually following up with a kind of behavior to avoid the event.



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.




8-2: The Senses


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.


Christine Ladd-Franklin: mathematician and psychologist who studied perception with well-known psychologists in Europe because American universities

                                        would not allow her to do so in the late 1800's.


     - Theory: color sensitivity developed in 3 stages.

                                1st stage: Achromatic: colorless vision

                                2nd stage: blue-yellow vision

                                3rd stage: red-green vision


She reasoned that red-green deficiency occurred most frequently because it developed last.  It was therefore, the most fragile of all the color zones.



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






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


The 6 Qualities of Smell








     - 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.




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



8-3: Perception


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.


- 4 principles of Gestalt:

* Closure :the tendency to group according to enclosed or completed figures rather than open or incomplete parts of patterns.

* Proximity: the tendency to group together elements that are close to each other.

* Similarity: the tendency to group together the elements that are similar in appearance. 

* Simplicity: foundation principle tendency to perceive a pattern in simplest most organized manner.



Dyslexia: is a reading disability with perceptual base. It is very common; about 10-20% of school population.


- 3 points:

        * people may reverse letters and numbers

        * hard time with left/right orientation

        * difficulty with coordination


- Famous Dyslexics:

        * Albert Einstein

        * Thomas Edison

        * Woodrow Wilson

        * Oprah Windfrey

        * Leonardo Decaprio

        * Cher

        * Tom Cruise

        * Danny Glover

        * Winston Churchill

        * General George Patton

        * George Burns

        * Whoopi Goldberg

        * Walt Disney

        * Alexander Graham Bell


Figure ground perception: the ability to distinguish properly between the figure and the ground.


        - fact: A single pattern can be perceived in more than one way. This demonstrates that we are not passive receivers of stimuli.

                     (sorry, Behaviorists of the world!)


        - use in hearing: we use what we hear to distinguish what is close and far away.  For instance, if listening to someone speak in a noisy room the voice is

                                    the “figure” and the noise is the “ground”


Perceptual inference: the phenomenon of filling in the gaps of what our senses tell us.  Sort of like assuming… and sometimes we assume incorrectly. 

                                   For example: if we are looking into the distance it looks like the road continues, but it may not.


- 4 points on perceptual inference:

* It is largely automatically and unconscious

* Due to past encounters with certain objects/events, we know what to expect in the future

* Largely depends on experience

* Humans are probably born with some of our ability to make perceptual inference… but most is learned


How we learn to perceive: Although a part of perception seems innate, we actually have to learn to perceive things correctly. 

                                           It is a basic aspect of the developmental process.


        - Aherns (1954): Did a study on how (and when) infants learn to perceive the human face.


                    * At under one month old: the child will smile at ANY nodding object the size of a human face, whether or not it has facial features.


                    * At 20 weeks: That same blank oval object will not make most babies smile, but if it has features drawn on it (or you use a mask) it will.


                    * At 28 weeks: Babies are more likely to smile at female face than a males.  (IE- just the opposite if the primary caregiver is male)


                      * By 30 weeks: most will smile more readily when the see a familiar face, than when they see one they don’t know.


* at 7 or 8 months: Babies can finally recognize different people by sight.


            *** Prior to this time, babies can tell the difference between people by smell.***


Importance of activity in learning to perceive: People and animals MUST be actively involved in their environments to learn depth perception.


- Held and Hein (1960): Passive and Active Kitten experiment:  Kittens were linked together on a “merry-go-round”.  One kitty

           was riding in a little car, which was being pushed by a kitty that was harnessed to it.  Each were encountering the environment

           in approximately the same way.    When they took “riding kitty” out of  his car and let him walk around he was not able to

           discriminate depth perception properly.


After he was active in the environment for a short time, he too could gauge depth.


            ** Conclusion:  One has to be active in the environment to fullylearn depth perception.


Valvo (1971): Experiments done with people who have been blind from birth, and had their sight restored through surgery, show that they have visual

                       sensations but, initially cannot tell the difference between a square and a circle.


Depth perception: ability to recognize distance and three-dimensionality.


        - Gibson and Walk (1960): Visual Cliff Apparatus experiment.

    Depth perception develops in infancy.  To prove this, the experimenters created the visual cliff.  They placed a baby on a box.  Connected to the

    box was a piece of plexi-glass that reached over to the box.  On the floor below it was the same pattern as on the boxes.  Although it looked

    similar, there was a “cliff” that could been seen. Babies placed on this would not crawl over the “edge” because they thought they would fall.

    This demonstrated that some depth perception is innate.


7 different external cues for depth percetion: People use many cues to perceive depth and distance.


                * size: the bigger the object looks, the closer it is. (bigger = closer)


                * interposition: object that is wholly shown, than if another object is interfered


                * shadow: yields information about shape and  size


                * texture density gradient: means that the further removed an object is, the less detail we can identify.  (farther = less details)


                * Arial perspective: makes far away objects look more blue.  (blue = farther)


                * atmospheric perspective: uses pollution in the air to gauge relative distance.      


                * linear perspective: suggests that parallel lines do meet somewhere in the distance.


- accommodation: occurs when the lens in your eye thickens as you look at nearby objects, and thins to view distant objects.


- 4 internal cues:

* convergence: is the process by which your eyes turn inward to look at nearby objects.


* retinal disparity: the differences between the images stimulating each eye.


* motion parallax: the apparent movement of stationary objects relative to  another that occurs when the observer changes position. 

                            Near objects seem to move greater distances that far objects.


* relative motion: when you are in a moving vehicle and the objects in the nearby field look as if they are moving in the opposite direction.


When we have learned to perceive certain objects in our environment, we tend to see them in the same way, regardless of changing conditions.


Constancy: the tendency to perceive certain objects in the same way, regardless of changing angles, distance, or lighting.


- Examples: people move closer to you but they don't become giants because the enlarging eye image and the distance information combine to

                  produce a perception of an approaching object that stays the same size.  (We make allowances for the closing distance.)


- 2 points:

1.) Distance information compensates for the enlarging eye image to produce size constancy.


2.) If the information about distance is eliminated, your perception of size of object begins to correspond to actual size of eye image.


     Example:  The real size of an airplane in the sky


Illusion: perception that misrepresents physical stimuli. (misrepresentations of reality)


        - Muller-Lyer illustration: The lines with arrows at each end, but with the arrows turned different ways making one look much longer.  (See page 125)


- mirages: atmospheric optical illusion where an observer sees a nonexistent body of water or image of distant object


* These are NOT illusions, hallucinations, or extrasensory perceptions, but natural, physical phenomena.



8-4: Extrasensory Perception and the Paranormal


Paranormal Phenomena Handout:


Extrasensory perception: is perception occurring independently of sight, hearing, or other sensory processes.


Rudolf Tichner: (1920's) a Munich ophthalmologist who was the first to coin the phrase "extrasensory perception."


9 types of ESP:


- telepathy: thought reading


- premonitions: dreams can predict future


- precognition: psych knowledge of something in advance of its occurrence. (another name for ESP)


- telekinesis: is the movement of objects by scientifically inexplicable means: moving objects by the power of the mind. (Many times called psychokinesis)


- Psychokinesis: production of motion in physical objects by the exercise of psychic or mental powers.  Psychokinesis maybe an apparent a technique

                            of mind over matter through invisible means. Examples of PK are movements of objects, bending of metals, and determining the

                            outcome of events. It can occur spontaneously and deliberately which indicates it is both an unconscious and conscious process.


- clairvoyance: The faculty of seeing into the future (sometimes called “second sight”), if it is not induced by drugs, trance, or any other artificial

                         means.  It is usually associated with precognition or recognition.


- retrocognition: the ability to see past events at which you were not present.


- psychometry: the ability to learn the history of an object.  It is similar to recognition, but is limited to the events surrounding a particular object.


- Astral Projection:  The ability to perceive environments or communications while psychically "at" a remote location by means of Out-of-body

                                experiences (also called spirit walking) or while in other dimensions.


Paranormal phenomena: any event or perception that involves forces or agencies that are beyond scientific explanation, but which nevertheless are

                                        mysteriously experienced.

        - Examples:  See handout.


        - Parapsychologist: researchers who study the supernatural


Other items of interest:


- medium: A predominantly Spiritualistic term applied to a person who regularly, and to a greater or lesser extent at  will, is involved in the

                production of psi ( used either as a noun or adjective to identify paranormal processes) in the form of mental and/or physical phenomena.


- post mortem communication: A communication or message said to be from a deceased to a living person, usually delivered through a medium.        

                                                Examples: John Edward, Silvia Brown and James Van Praagh are popular psychic mediums.


- aura: a field of subtle, multicolored, luminous radiations said to surround living bodies as a halo or cocoon; the term is occasionally used to refer

            to the normal electromagnetic field forces surrounding the body.



J.B. Rhine: Probably the most famous parapsychologist who began a series of precise statistical tests in ESP during the 1930's at Duke University. 

                    His results were never completely proven... although they weren't disproven either.


- Zenner Card experiment (1930's): Experiment in telepathy.

         In the experiment one person is the "sender" and one the "receiver".  They used a 25 card deck.  Each of 5 cards has a different symbol on it.

         (wave, star, square, circle, and a cross).  The sender would "send " the image on the card, drawn at random, to a receiver in another room.  The

         receiver then tells what image he/she is "receiving."


     * This test has been done thousands of times since, and numerous people have scored above average. (Hundreds of them in Ms. Weid's classes alone!)


        * You can get 5 correct out of 25 guesses on just dumb luck.


Uri Geller: A very popular psychic during the 1970's.  He was known as the telekinetic spoon bender.  He could concentrate on a metal spoon (silver or steel),

                  and it would bend when looked at later.  No one could explain how he could do this, except for telekinesis. "Uri Geller is the world's most

                  investigated and paranormalist. Famous around the globe for his mind-bending psychic powers, he has led a unique life shrouded in debate

                  and mystery. He is also related to Sigmund Freud." - from the Uri Geller website. (Now there's an ego booster for ol' Uri!  Check that one out.) 


- Science has not been able to explain Uri's ability.


- telekinesis: is the movement of objects by scientifically inexplicable means: moving objects by the power of the mind.


Edgar Cayce: At the age of twenty-one he developed a gradual throat paralysis which threatened the loss of his voice. When doctors were unable to find

                      a cause for his condition, Cayce entered the same hypnotic sleep that had enabled him to learn his school lessons years before. In that state,

                      he was able to recommend a cure, which successfully repaired his throat muscles and restored his voice. It was soon discovered that he could

                      do the same for others.


                    For most of his adult life, Edgar Cayce was able to provide intuitive insights into nearly any question imaginable. When individuals came to him

                    with a question, he would place himself into a self-induced sleep state. While in that state he could respond to virtually any question asked.

                    His responses have come to be called "readings". Today his psychic readings constitute one of the largest records of intuitive information to

                    emanate from a single individual.


                    For many years the information dealt mainly with medical problems. Eventually the scope of his readings expanded to include such topics as     

                    meditation, dreams, reincarnation, and prophecy. Cayce gave over 14,000 readings on more than 10,000 different topics to people all over the



                                                                *** Scientifically, he was considered by many to be a hoax.



Noreen Renier: As a police consultant the "psychic detective," has assisted law enforcement officials in 38 states and six foreign countries in cracking

         seemingly unsolvable homicides and other crimes.  She is perhaps the well-known psychic detective who has worked on over 400 unsolved cases.  She

         has a unique understanding of both the police and the paranormal.


         Her methods include psychometry and remote viewing.  As a psychometrician, she touches objects the victim wore or suspect left behind.  Renier

         believes that objects emit a field of energy which can be "read".   This energy-field carries information, images, visions, feelings, etc.

         Remote Viewing is a technique in which Renier becomes another person; seeing, hearing and feeling the world through the senses of others.



Charles Tart: Researcher who did experiments with a four light box.  He screened over 1,500 college students in this study.  People would guess which

                       light would light up at random.  They were right about 26.8% of the time.  His studies had some major problems, especially the fact that he

                       had unsupervised graduate students collect the data.  His "results" probably hurt the ESP debate more than it helped it.


ESP - fact or fake?


        6 reasons to disbelieve in ESP:

- You can get 20% (5 out of 25 guesses) right just by luck.

- Experimenters who believe in ESP sometimes make errors supporting their belief.

- Intentional Fraud

- Findings can be highly unstable. (You can't depend on replicating another scientist's results every time.)

- When strict controls are used in an ESP experiment, there is little likelihood of demonstrating ESP.

- ESP responses are best generated in highly emotional situations.

- ESP is nothing more than coincidence.


6 reasons to believe in ESP:

- A person may have have had a "confirming event."  (Because the coincidence is so striking and unusual, it is often interpreted as non-coincidental.)

- For some people, believing in ESP fulfills some personal need.  (It may, for example, give them a sense of control in their lives that they otherwise lack.)

- Belief in ESP opens up the possibility of survival after death and implies that we all have undeveloped powers. 

- Many unusual events that seem inexplicable.

- ESP usually occurs spontaneously in conditions which are not scientifically controlled.

- Belief in the fact that what science knows about the nature of universe is incomplete