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
•
• 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
• 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
COLOR VISION
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 redgreen 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 blackwhite
• 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.