SENSATION AND PERCEPTION Chapter 3

THE NATURE OF SENSATION Section 1

• Sensation: smells, sights, sounds, taste, balance, touch, and pain• Experience of sensory stimulation

• Perception: mental process of soring, identifying, and arranging the bits into meaningful patterns • Process of creating meaningful patterns form raw sensory information

THE BASIC PROCESS

• Sequence of events that produces a sensation• Step 1: there needs to be some form of energy that stimulates a receptor cell—a specialized cell that responds to a particular type of energy—in one of the sense organs • Ex: light waves or vibrations to the eye or ear

• Step 2: if the stimulus is strong enough the receptor sends a signal to the appropriate part of the brain • Step 3: Sense what is around us• Ex: Seeing or hearing

• How does the brain distinguish between sights and sounds, sensations of touch and balance?• Sensory Discrimination • Begins in with receptor cells that are connected to specialized neural pathways• Sensory messages enter the brain on different channels • EX: bright lights sends a more rapid firing neuron

and dim lights have a less rapid firing neuron

SENSORY THRESHOLD

• The energy reaching a receptor must be intense enough to have a noticeable effect• Absolute Threshold: the minimum intensity of physical energy requited to produce any sensation

• Under ideal conditions… • Taste: 1 gram of salt in 500 liters of water• Smell: 1 drop of perfume in a 3 room apartment • Touch: the wing of a bee falling on your cheek form 1 cm of height• Hearing: the tick of a watch 20 feet away in very quite conditions • Vision: a candle flame seen from 30 miles away on a clear dark night

• Absolute Thresholds vary depending on the level and nature of on going sensory stimulation • Ex: when you walk into a dark movie theater you cant seen anything other than the screen until your eyes gradually adjust when your eyes come accustom to the darkness • Sensory Adaptation: an adjustment of the senses to the level of stimulation they are receiving

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•With our senses what we notice most is the change…change form no stimulation to stimulation or less to more• Difference Threshold or Just noticeable Difference: the smallest change in a stimulation that can be detected 50% of the time • Varies from person to person

• Ernest Weber•Weber’s Law: principle that the Just Noticeable Difference for any give sense if constant fraction or proportion of the stimulus being judged• Ex: Hearing is very sensitive and an detect a change in sound that is 1/3 of 1%

SUBLIMINAL PERCEPTIONS

• Story goes….• 1950’s a movie theater in Fort Lee, NJ added messages like “drink coke” and “eat popcorn” between frames of the movie Panic • Although the messages where flashed to quickly for the moviegoers to notice them consciously• Legend has it that soda and popcorn sales increased dramatically

• In actuality…• There was no change in sale• According to a survey nearly 2/3 of Americans believe hat

advertisers put hidden messages and images in their advertisements to increase sales of their products

• Can people influence by information of which they are not consciously aware?• YES!• Ex: experimental group was exposed to competition and the

control group was exposed to a list of neutral words • Words were flashed on a screen too rapidly for participants to

identify them• Late all participants played a game and the experimental

group was particularly Competitive

• Does not mean that people automatically or mindlessly “obey” subliminal messages• The exact opposite seems to be true—in independent scientific studies it has been shown that hidden messages outside the laboratory have no significant affect on behavior • But the mind can play trick on itself… another studies showed that a group of volunteers listened to memory improvement tapes • Half of them said it worked on them and they were remembering more but• They were actually listening to self improvement tapes

EXTRA SENSORY PERCEPTION

• People claim to have extra power of perception know as Extra Sensory Perception or ESP• Refers to a variety of phenomena including • Clairvoyance: awareness of an unknown object or event• Telepathy: knowledge of someone else's thoughts or feelings • Ex: reading someone's mind

• Precognition: foreknowledge of future events• Ex: seeing into the future

• Parapsychology: the study of the operation of ESP and other psychic phenomena • Much of the research into ESP has been criticized for…• poor experimental design• failure to control for dishonesty• selective reporting of results• inability to obtain replicable results

• Not all psychologists discount ESP, 34% of all psychologists accept ESP as either an established fact or a likely possibility

VISION Section 2

THE VISUAL SYSTEM

• How we see• Light enters through the cornea—the transparent protective coating over the front part of the eye• It then passes though the pupil—a small opening in the iris which light enters the eye

• Iris: the colored part of the eye• In very bright light the iris contract to make the pupil smaller to protect the eye and make us see better in bright lights• In dim light it widens and lets in as much light as possible to see best

• Inside the pupil, light moves through the lens—transparent part of the eye inside the pupil that focuses light into the retina • Retina: lining of the eye containing receptor cells that are sensitive to light

• The lens changes shape to focus on objects that are closer and farther away• Normally, the lens is focuses on the middle

• Blind spot: the place on the retina where the axons of all the ganglion cells leave the eye and where there are no receptors

• On the retina directly behind the lens, lies a depressed spot called the Fovea• Occupies the center of visual field, and images are the sharpest in focus here•When we want to examine something in fine detail, we bring it close to the fovea

• Receptor Cells• Each retina contains a receptor cell responsible for vision • Theses cells are only sensitive to a fraction of the spectrum of electromagnetic energy• Includes light—the segment of the electromagnetic spectrum we can see

• 2 kinds of receptor cells—rods and cones• Rods: receptor responsible for night vision and perception of brightness• Cones: receptor responsible for color vision

• Rods and cones connect to specialized neurons called bipolar cells • Neurons with only one axon and one dendrite

• The one –to-one connection between cones and bipolar cells allows for maximum visual acuity • Visual Acuity: ability to distinguish fine details visually

• Adaptation • The process by which our sense adjust to different levels of stimulation• Dark Adaptation: increased sensitivity of the cones and rods in darkness• Ex: After sitting in the dark taking notes and the lights are turned on your eyes are sore and sensitive to light

• Light Adaptation: decreased sensitivity of rod and cones in bright light• EX: When you are outside all day in bright light and it does not affect you

• Afterimage• Sense experience that occurs after the visual stimulus is removed

• Afterimage Test• Stare continuously, without blinking at the yellow dot on the left image for 20 seconds• Then look at the white square to the right•What do you see?

• From eye to brain• We don’t actually “see” with our eyes but instead

with our brains• Messages from the eye must make there way to the

brain for sight to occur• The rods and cones are connected to bipolar cells in

many different numbers and combinations • The bipolar cells then hook up with ganglion cells—

neurons that connect the bipolar cells in the eye to the brain • The axons of the ganglion cells join together to form

the optic nerve—bundle of axons of ganglions that carries neural messages form eye to brain

• After they leave the eye, these fibers that make up the optic nerves, separate and some cross to the other side of the bead at the optic chiasm• Optic Chiasm: point near the base of the brain where some fibers in the optic nerve from each eye cross to the other side of the brain •What we see with our right eye is processed to our left occipital lobe and what we see with our left eye is processed in the right occipital lobe • See page 107 of textbook

COLOR VISION • Properties of Color• Psychologists call different

colors hues and what hues you see depends on the wave length of light reaching your eyes• The vividness or richness of a

hue is called saturation • Brightness: the nearness of a

color to white opposed to black • Hue, saturation, and brightness

are 3 separate aspects of our experience of color• Most people can identify 150

distinct hues but graduations of saturations and brightness allows us to see many variations of that hue

THEORIES OF COLOR VISION • There are only 3 colors—red, yellow and blue• Hermann von Helmholtz and the Trichromatic Theory • Proposed a theory of color vision based on Additive Color Mixing—mixing lights of different wavelengths to create new hues• His explanation for color vision is know as Trichromatic Theory (3 color theory)• The theory of color vision that hold that all color perception derives from 3 different color receptors in the retina• Usually red, green and blue receptors

• Also explains how 3 primary colors can be combined to make other hues and accounts for people with color blindness

• Trichromats: people who have normal color vision• Color Blind: partial or total

inability to perceive hues• 10% of men and 1% of

women• Dichromats: people who

are blond to either red-green or yellow blue

• Monochromts: people who are totally color blind and only see in shades of light and dark • Extremely rare

• Edward Hering and the Opponent Process Theory • Alternate theory of color vision that helps to explain monochromats• 3 pairs of colors yellow-blue, red-green, and black-white• Yellow- blue and red-green determine the hue you see and black-white determines the brightness of the color•We can either see something that is yellow or blue but not yellowish blue

• Also explains afterimages

COLOR VISION IN OTHER SPECIES

•Many animals have color vision, but the colors they see varies• Humans and most primates are trichromats and most other mammals are dichromats • Hamsters, rats, squirrels, and other rodents are completely color blind, or monochromats• Some animals see colors we cannot see• Ex: Bees see Ultraviolet light• Bees see flowers with white petals that look drab to us as flash to them like neon signs

HEARING Section 3

SOUND• Sound: our brain’s interpretation of the flow of air molecules pounding against our eardrum• Sound Waves: how sound travels• Frequency: how often a wave occurs • Hertz: the unit of measurement for wave cycles• Pitch: how high or low a sound is • Amplitude: the height of a wave• Along with frequency determines how loud a sound is•Measured in decibels

• 80+ Decibels potential ear damage• Concerts,

lawnmower, subway train, headphones at full volume

• 130+ pain threshold• Revolver

firing a close rang

THE EAR

• Hearing begins when sound waves strike the eardrum and cause it to vibrate• The vibration causes 3 tiny bones in the middle ear to hit each other in sequence and thus carry vibrations to the inner ear• Hammer, anvil and stirrup

• The stirrup (last bone) is attached to the Oval Window—membrane across the opening between the middle and inner ear that conducts vibrations to the cochlea • Cochlea: part of the inner ear containing fluid that vibrates, which in turn causes the basilar membrane to vibrate—snail shaped

• The cochlea is divided lengthwise by the basilar membrane—vibrating membrane in the cochlea of the inner ear; it contains sense receptors for sound• Lying on top of the basilar

membrane, and moving in sync with it is the organ of Corti—contains the receptor cells for hearing• Thousands of tiny hair cells • The brain pools the

information from thousands of these cells to perceive sounds

• Neural Connections• Each ear sends messages to both cerebral hemispheres• The primary destination for the auditory messages are the temporal lobes

THEORIES IN HEARING

• The more neurons activated, or fired the louder the sound• 2 basic theories for pitch—place theory and frequency theory• Place Theory: pitch is determined by the location of greatest vibration on the basilar membrane • High frequency/ pitch sounds are at the base • Low frequency/ pitch sounds are at the opposite end

• Frequency Theory: pitch is determined by the frequency with which the hairs in the cochlea fire• If the hair bundle is pulled or pushed rapidly it is a higher frequency/ pitch sound• Volley Principle: Auditory neurons fire in sequence: one neuron fires and then the next and so on. By then the first one has time to recover and can fire again• Send a more rapid series of impulses than just

one neuron

HEARING DISORDERS• Estimated 28 million Americans suffer from partial or total

deafness• Injury, infections, explosions and long term exposure to

loud noise can harm your hearing and cause partial to total deafness• 30 million people are exposed to damaging noise levels

daily• Ex: leaf blowers, chainsaws, jet planes, headphones

and personal stereos • People 45-65 are more likely to experience natural

hearing problems • Most cases of deafness in old age is result of

undetected ear infections in childhood, exposure to noise

• People with irreversible damage can use devices to increase their hearing• Hearing aids• Cochlear implants can help people with total deafness due to cochlear damage

EXIT SLIP: YOUR HEARING ABILITY

• Test 1: How old are your ears?• After listening to the recording write down how old your ears are.

• Test 2: Basic Hearing Test • Listen for the first tone you can hear and write down what the screen says about your hearing.

•Question 1: Do you think you have good hearing?

•Question 2: Do you think you are contributing to your hearing impairments?

THE OTHER SENSES Section 4

SMELL• Smell is the most primitive •We feel that most smells are either alluring or repulsive…we rarely think of a smell as neutral •We either like it or not

• A mere whiff can trigger sudden, unexpected, emotionally charged memories• Romance, childhood memory, special memory etc.• Smells evoke powerful memories because some of the nerves in our nose are directly connected to parts of the brain that are responsible for emotion and memory

•Many use odors to distinguish between good and bad, safe and unsafe• Ex: smell of smoke and fire, sour milk and being expired

• Smell undergoes adaptation that why you may not smell the perfume/cologne you sprayed hours ago when other still can

• Detecting Common Odors • Sense of smell is activated by complex protein produced in a nasal gland • As we breathe a fine mist of protein called Odorant Binding Protein (OBP) is sprayed through the tip of the nose

• The protein combines with airborne molecules that activate receptors located high in each nasal cavity in a patch of tissue called the Olfactory Epithelium—nasal membranes containing receptor cells sensitive to odors.• The axons from these million receptors go directly to the Olfactory blub—smell center of the brain • From there it is routed to the temporal lobes resulting in awareness of the sent

• Communicating with Pheromones• Many animals use chemicals as means of

communication • Invisible, sometimes, odorless molecules called

Pheromones secreted by glands or in urine can have powerful effects on animal behavior• Pheromones stimulate receptors in the Vomeronasal

Organ—location for the pheromones in the roof of the nasal cavity • Sends messages to a second olfactory bulb specially

designed to interpret pheromonal communications

• Pheromones also provide information about another animal’s identity• When an animal sniffs another member of their species

they can identify the last time the animal ate, how dominate they are, if they are healthy, and their gender

TASTE

• To understand taste, we must first distinguish it form flavor • flavor come from a complex mixture of taste and smell• EX: when you hold your nose and eat something it loses most of

its flavor but you can still identify if it is bitter, salty, sweet, or sour • You can taste it but not identify the flavor

• Taste Buds: structure on the tongue that contain receptor cells for taste • Found on the tip, sides and back of tongue • Tip= sensitive sweetness and saltiness• Sides= sourness• Back= bitterness

• The number of taste buds decrease with age• Taste buds are embedded in the tongue’s papillae—small bumps on

the tongue that you can see that contain taste buds

KINESTHETIC AND VESTIBULAR SENSES

• Kinesthetic Senses• Kinesthetic Senses provides information about the speed and directions of our movements • Specialized never endings, called Stretch Receptors, are attached to muscle fibers• Different nerve endings, know as Golgi Tendon Organs, are attached to tendons• connect muscles to bone

• Vestibular Senses• Gives us clues about our orientation or position in space, tells us which was is up and down• Vestibular Sacs: sacs in the inner ear that sense gravitation and forward backward and vertical movement

SENSATIONS OF MOTION •We are most aware of our Vestibular senses when we experience motion sickness• Certain kinds of motions, such as riding ships, cars and airplanes, trigger strong reactions in some people

• To avoid motion sickness: • Avoid reading while traveling in a car, boat or plane• Don’t sit in a seat facing backwards• Try to sit in the front seat and look at distant objects• Open a window•Medications

THE SKIN SENSES

• Touch plays a crucial role in human development • Ex: premature babies use to never be touched because they were considered fragile • NOW—studies show that babies who are held and swaddled more gain more weight, were more responsive to humans and were released from the hospital sooner

• Our skin is the largest sense organ • Protects us from the environment, holds in body fluids, and regulates our internal temperature

• Various skin receptors give rise to sensations of pressure, temperature and pain • Face and fingertips are super sensitive whereas your feet, legs and back are not

• Sensory adaptation•When you put on clothes you feel them at first but overtime you don’t feel them touching your skin

PAIN• Pain serves as a warning signal, telling us whether we have been injured or something is wrong • Also tells us that out body is fighting back and informs the body’s defense when they may be reacting too much and signals then to stop• Phantom Limbs •When a person has a limb amputated they still “feel” that arm like it was never removed• Eventually the brain realizes its not there and it goes away

• Individual Differences• People vary in their pain threshold (how much stimulation is

needed to feel pain) and pain tolerance (the amount of pain they can cope with)• Gate Control Theory: the theory that a “neurological gate”

in the spinal cord controls the transmission of the pain messages to the brain• When the gate opens you feel more pain • “gate” opens and closes based on the interaction of

sensory nerve fibers • Biopsychosocial Theory: theory that the interaction of

biological, psychological and cultural factors that influence the intensity and duration of pain • The amount of pain we feel is based on our biology and

how we are raised

PERCEPTION Section 5

PERCEPTIONAL ORGANIZATION

• Important pieces of perception is distinguishing figures from the ground against which they appear • Figure: a thing that

stands apart from a background• Ground: background

against which a figure appears

• Sometimes there are not enough cues and you cannot tell what is a figure and the ground

PERCEPTIONAL CONSTANCIES

• Refers to the tendency to perceive objects as relativity stable and unchanging despite changing sensory information • Ex: the white house looks like the white house no matter how close we are to it and the time of day

•We tend to perceive familiar objects at their true size regardless of the size the image they cast• Ex: seeing a women who looks 5’4 and knowing that she is not 3 ft tall

• Size Constancy: the perception of an object as the same size regardless of the distance from which we view it • Shape Constancy: tendency to see an object as the same

shape no matter what angle it is viewed from • You perceive a plate to be a circle even when it is angled

away and doesn’t like a circle • Color Consistency: an inclination to perceive familiar objects

as retaining their color despite changes in sensory information • when you imagine an apple it is usually red NOT green or

yellow

PERCEIVING DEPTH AND DISTANCE

• The ability to judge distance and depth is critically important to move freely in the environment •When you go to pick up a pencil you automatically judge how far to extend your arm•Monocular Cues: visual cues requiring the use of one eye• Binocular Cues: visual cues that require the use of both eyes• Allows us to make more accurate judgments about distance and depth

• Locating Sound•We draw on monaural and binaural cues to locate a source of sound •Monaural Cues: using one ear• Binaural Cues: using both ears•Most accurate

PERCEIVING MOVEMENT

• Involves both visual information and messages from the muscles around the eyes as they follow an object • Real Movement• Physical displacement of an object from one position to another • If you turn your head while looking at objects you will assume that they are in motion but the muscles around your eyes are what determines that they are motionless

• Apparent Movement• An illusion that occurs

when we perceive movement in objects that are actually still • Test: While Focusing on

one of the circles move your head back and forth• What do you see? What

is happening?

VISUAL ILLUSIONS

• Visual Illusions further demonstrate the ways in which we use a variety of sensory cues to create perceptual experiences• Perceptual Illusion: illusion due to misleading cues in stimuli that give rise to inaccurate ort impossible perceptions

VISUAL ILLUSIONS

• Which Arrow line i is longer? Line A? or Line B?

• Does this triangle look 2-D?

• Not drawn flat on paper?

• Which figure is larger?

• Which yellow Line is longer? Top or bottom?

OBSERVER CHARACTERISTICS:INDIVIDUAL DIFFERENCE AND CULTURE

• Perception is a combination of information from our senses, past experiences, and wiring of our brains •Motivation• Our desires and needs shape our perceptions• People in need are more likely to perceive something that they think will satisfy them

• Values• The strength of a persons values shape the strength of their perceptions

• Expectations• Preconceptions about what we are suppose to perceive may influence perception by causing us to delete, insert or modify what we see

• Experience and Culture• Cultural background influences people perceptions

• Personality • Individual personalities influence our perceptions

ENDURING ISSUES: HOW DOES ETHNICITY INFLUENCE PERCEPTION?

• All normal human beings have the same sense organs and perceptual capacity. Yet our individuality—our motives, values, expectations, cognitive style and cultural preconceptions—influence what we perceive. •With focus on individual differences in this section.

• But, as we read, to what degree do people’s sensory and perceptual experiences differ depending on their race, culture, or gender?

HOMEWORK: DO PERCEPTIONAL EXPERIENCES REFLECT THE OUTSIDE WORLD?

• After reading this chapter do you think you see things more as the “retina image” (exactly as they are) or do you think that you perceive (understand) things based more on how it affects your thoughts, emotions, motives, attitudes, values, and personality? •What examples would you select from the chapter to make your point most effectively? •Write a full paragraph of 6-8 sentences to support your point.