IV. Sensation and Perception (6–8%)
Everything that organisms know about the world is first encountered when stimuli in the environment
activate sensory organs, initiating awareness of the external world. Perception involves the
interpretation of the sensory inputs as a cognitive process.
AP students in psychology should be able to do the following:
• Discuss basic principles of sensory transduction, including absolute threshold, difference threshold,
signal detection, and sensory adaptation.
• Describe sensory processes (e.g., hearing, vision, touch, taste, smell, vestibular, kinesthesis, pain),
including the specific nature of energy transduction, relevant anatomical structures, and specialized
pathways in the brain for each of the senses.
• Explain common sensory disorders (e.g., visual and hearing impairments).
• Describe general principles of organizing and integrating sensation to promote stable awareness of
the external world (e.g., Gestalt principles, depth perception).
• Discuss how experience and culture can influence perceptual processes (e.g., perceptual set, context
effects).
• Explain the role of top-down processing in producing vulnerability to illusion.
• Discuss the role of attention in behavior.
• Challenge common beliefs in parapsychological phenomena.
• Identify the major historical figures in sensation and perception (e.g., Gustav Fechner, David Hubel,
Ernst Weber, Torsten Wiesel).
I. Define
A. Sensation- Process by which we receive information
1. Begins with a stimulus
a. Any detectable input from the environment.
b. What is detectable depends on who or what.
2. Includes absorption
3. Involves coordination among receptors, neural pathways, and sensory
processes. Involves the neural connections in the brain.
4. Possible through sight, hearing, touch, smell, taste as well as through
kinesthetics and vestibular system.
5. Sensory systems are tied to perception.
B. Perception- our interpretation of
C. Psychophysics- Study of how physical
1. Gustav Fechner- most significant figure.
II. Thresholds - a dividing point between energy levels that do and do not have a
detectable point. (like a light that turns on at dusk.) At what point are we able to
detect that a stimulus is present?
A. Absolute threshold- The point at which a stimulus
1. Given a particular stimulus, the minimum intensity of stimulation
needed to produce a sensation at least 50% of the time.
2. Subliminal perception- information below the threshold- Studies
have shown it does influence people- when flashed a positive slide and
then shown a picture of a person describe them more positively and
vice versa.
B. Difference threshold or
1. Minimum change in the intensity of
2. Weber’s law- states that there is a constant proportion (not amount)
between the threshold and the stimulus for each sense quality. For
example we notice an inch that is added to a goldfish more than an
inch that is added to an elephant. ∆S = K
S
**∆S = change in the intensity of the stimulation
S= the stimulation already there
K= the constant value for each sensory quality
a. This means that the amount of change in the stimuli that is
necessary in the stimulation depends on what level is
present of stimulation.
b. Some senses are
c. JND stands for the Just Noticeable Difference- it is the
difference
3. Signal Detection theory- Proposes that the detection of stimuli
involves
a. Term was prominent in the 1960s applied to detection of
radar and soviet missiles.
b.
Present
Absent
Responder
says a
stimulus is
present
Responder
says a
stimulus is not
present
c. Liberal responders prefer to say yes
d. This begins to beg the question- what are the factors that
influence our sensory judgment.
III. Receptors
A. Environmental Information (stimuli) exists in many forms:
1. Air vibrations, gases, chemicals, tactile pressure
2. Body receives the info through specialized cells.
a. Receptors work as transducersb. E.g.- taste buds on the tongue convert chemical signals to a
pattern of electrochemical activity sent to the brain.
B. Receptor sensitivity is subject to change.
1. Sensory adaptation- Gradual decline in sensitivity to
a. Decline in receptor activity
b. E.g.-
2. Habituation- is all in your interpretation
a. Decrease in sensory sensitivity at
b. Different from sensory adaptation in that responsiveness
can reappear if stimulation level is increased or decreased.
c. Example
Lesson 2
Vision
Sense Organ
Universal Energy Source
Human Threshold
Extra info
Label the Eye Diagram #2
Human Anatomy
Read the definitions, then label the eye anatomy diagram below.
Cornea - the clear, dome-shaped tissue covering the front of the eye.
Eyebrow - a patch of dense hair located above the eye.
Eyelash - one of the many hairs on the edge of the eyelids.
Eyelid - the flap of skin that can cover and protect the eye.
Iris - the colored part of the eye - it controls the amount of light that enters the eye by
changing the size of the pupil.
Lens - a crystalline structure located just behind the iris - it focuses light onto the retina.
Optic nerve - the nerve that transmits electrical impulses from the retina to the brain.
Pupil - the opening in the center of the iris- it changes size as the amount of light changes
(the more light, the smaller the hole).
Retina - sensory tissue that lines the back of the eye. It contains millions of
photoreceptors (rods and cones) that convert light rays into electrical impulses that are
relayed to the brain via the optic nerve.
Tear - clear, salty liquid that is produced by glands in the eyes.
Vitreous - a thick, transparent liquid that fills the center of the eye - it is mostly water
and gives the eye its form and shape (also called the vitreous humor).
A. Characteristics of light.
B. Color theories
1. Young- Hemholtz Trichromatic Theory
2. Opponent Processing Theory
C. Color blindness- Color deficiency1. Dichromacy- the person can distinguish only between 2 colors pairs
2. Monochromacy- completely color blind- very rare condition.
Lesson 3
Audition
Sense Organ
Universal Source of
Energy
Human Threshold
Label the Ear Anatomy Diagram
Additional Info
Human Anatomy
Sound is collected by the pinna (the visible part of the ear) and directed through the outer
ear canal. The sound makes the eardrum vibrate, which in turn causes a series of three
tiny bones (the hammer, the anvil, and the stirrup) in the middle ear to vibrate. The
vibration is transferred to the snail-shaped cochlea in the inner ear; the cochlea is lined
with sensitive hairs which trigger the generation of nerve signals that are sent to the brain.
Read the definitions below, then label the ear anatomy diagram.
anvil - (also called the incus) a tiny bone that
passes vibrations from the hammer to the stirrup.
cochlea - a spiral-shaped, fluid-filled inner ear
structure; it is lined with cilia (tiny hairs) that move
when vibrated and cause a nerve impulse to form.
eardrum - (also called the tympanic membrane) a
thin membrane that vibrates when sound waves
reach it.
Eustachian tube - a tube that connects the middle
ear to the back of the nose; it equalizes the pressure
between the middle ear and the air outside. When
you "pop" your ears as you change altitude (going
up a mountain or in an airplane), you are
equalizing the air pressure in your middle ear.
hammer - (also called the malleus) a tiny bone that
passes vibrations from the eardrum to the anvil.
nerves - these carry electrochemical signals from the inner ear
(the cochlea) to the brain.
outer ear canal - the tube through
which sound travels to the eardrum.
pinna - (also called the auricle) the
visible part of the outer ear. It
collects sound and directs it into the
outer ear canal
semicircular canals - three loops of
fluid-filled tubes that are attached to
the cochlea in the inner ear. They
help us maintain our sense of
balance.
stirrup - (also called the stapes) a
tiny, U-shaped bone that passes
vibrations from the stirrup to the
cochlea. This is the smallest bone in
the human body (it is 0.25 to 0.33
cm long).
Complexity
Frequency
Amplitude
C. Characteristics of sound
D. Audition theories
Place Theory
Frequency Theory
Volley principle
•Difference frequencies
cause vibrations at different
locations along the basilar
membrane
•Increased frequency causes
maximum vibration at t
stirrup end, and decreased
frequency at the other end
•Assumes hair cells respond
independently and different
sets of hair cells are vibrated
by different sound
frequencies
•Explains lower pitch
•Basilar membrane vibrates
at the same frequency as
the sound wave. Sound
wave of 100 hrtz means the
hair cells vibrate at 100
times per second
•Neurons can’t fire at more
than 1000 times per second
•Holds that groups of
auditory nerve fibers fire
neural impulses in rapid
succession, creating volleys
of impulses
•This means that while some
are firing others are
“reloading”
E. Hearing Loss
1. Conduction hearing loss (ear drum damage, bones become brittle
and fuse together)2. Sensorineural hearing loss (this is what rock musicians experience)-
F. Sound Localization- how we identify where a sound is coming from. One
ear receives information
Lesson 4
Gustation
Sense Organ
Energy Source
Human Threshold
Extra info
A. 5 basic taste qualities- receptors are sensitive to these
1.
2. Linda Bartashuk- Yale Medical- a taste research. Discovered there is
no taste map (it was previously believed that different tastes qualities
lay on different parts of the tongue)- the original German research was
mistranslated. There is an evolutionary value to our taste. For
example, bitterness helps us to know that there might be a poison.
3. Supertasters versus nontasters
4. Some basic taste preferences appear to be innate and automatically
regulated by physiological mechanisms- newborns react positively to
sweet and salty- and negatively to strong concentrations of bitter or
sour tastes.
B. Other influences on taste- smell, texture, temperature. What happens when
you have a cold? You probably have more difficulty tasting because you
can’t smell the food.
Olfaction
Sense Organ
Universal
Source of
Energy
Absolute
Threshold
Additional Info:
A. Olfactory EpitheliumOlfactory Cilia1. Nasal cavity2. Olfactory bulb3. Gases- Olfactory cells in this membrane are stimulated
4. For stimulus to be smelled, it must be dissolved.
B. Pheromones- sex attracting odor-
Somosthesis
Sense Organ
Universal Energy
Source
Absolute Threshold
Additional Info
A. Kinesthesis
B. Vestibular senses-also called equilibratory senses
Lesson 5
I. Perceptual processes
A. Attention- process in which consciousness is focused on particular stimuli
1. Selective attention- ability to focus on one stimulus while
2. Divided Attention- ability to respond to more than
a. If you are using two different senses, it is easier to divide
your attention
b. It is harder to divide our attention the older we get
B. Perceptual organization- process which group smaller units of the
perceptual world into larger units.
1. Figure-ground- tendency to organize the visual field into objects that
stand apart from the
2. Gestalt- we tend to organize our perceptions
a. Principles of Gestalt organization
i.
Similarity- stimuli that are similar in size, shape,
color or form tend to be grouped together
ii. Proximity- Stimuli that are near each other are
grouped together
iii. Continuity- Perceptions tend toward simplicity or
continuity- lines tend to be seen as following the
smoothest path- line interrupted by an overlapping
object are seen as belonging together if the result in
straight or gently curving lines when connected
iv.
Closure- figures that have gaps in them are seen as
completed and perceived as recognizable objects.
v.
Simplicity- every stimulus pattern is perceived in
such a way that the resulting structure is as simple
as possible
vi.
Phi Phenomenon- Perceived motion when the
object is, in fact, stationery. (when two lights are
placed in a dark room and flashed alternately, one
light moving back and forth is perceived) Theatre
marquees- when words appear to move from one
side to the other as different combinations of
stationary lights are flashed on and off.
II. Perceptual abilities- our brains interpret stimuli in such a way as to impose
stability on the environment. We override the literal sensory messages with prior
knowledge.
A. Perceptual constancy
1. Size constancy- we see a car as being the same size in spite of the
fact that the image on the retina becomes smaller as the car moves
away from us.
2. Shape constancy- gives us the message that the car’s tires are still
round although the retina has the image of an ellipse as the car turns a
corner.
3. Brightness or lightness constancy- objects appear to stay the same
brightness despite changes in the amount of light falling on them. If a
cloud cover changes the light in the vicinity, we do not see the car as
being less white than it was
B. Binocular Cues- our eyes and brain work
1. Binocular disparity- (retinal disparity) The retina of each eye gets
2. Convergence- involves the interpretation of
C. Monocular cues- cues provided by one eye
1. Linear perspective- parallel lines appear to converge on the horizon
(RR tracks)
2. Relative Size- close objects appear larger
3. Overlap or interposition- objects that are overlapped or partially
concealed by other objects will appear farther away
4. Gradient of texture- objects that are closer have greater detail or
texture than those farther away
5. Arial perspective- closer objects are bright and sharp- distant objects
are pastel and hazy
6. Relative motion or motion parallax- when moving our head from
side to side, nearby objects appear to move more than distant objects,
far objects appear to move slower than nearby objects
7. Height on plane- objects that are closer appear to be lower in the
field than objects that are farther away.
8. Accommodation- lens of eye must bend or adjust to bring to focus
objects that are relatively close.
D. Pattern Perception- enables us to recognize faces, objects, words and other
organized patterns in the environment.
1. Bottom up processing2. Top-down processingE. Other information
1. Perceptual set- mental predisposition- such as motivation, values,
expectations, cognitive style, experience and culture and personality
can all effect what we see.
2. Perceptual illusion- occur because the stimulus contains misleading
cues that distort the perceived size or orientation of common objects
giving rise to inaccurate or impossible perceptions