CHAPTER 8: SENSATION AND
PERCEPTION
SECTION 1: SENSATION
WHAT IS SENSATION?
• Def: what occurs when
a stimulus activates a
receptor
• Stimulus: an aspect of
or change in the
environment to which
an organism responds
SENSATION CONTINUED
• Perception:
organization of sensory
info into meaningful
experiences
• Psychophysics: study of
the relationships
between sensory
experiences and the
physical stimuli that
cause them
THRESHOLD
• Absolute threshold: the
weakest amount of a
stimulus that a person
can detect half the time
• Humans have a very
limited range
SENSORY DIFFERENCES
• Difference threshold:
the smallest change in a
physical stimulus that
can be detected
between 2 stimuli
• Just Noticeable
Difference (JND): the
smallest increase or
decrease in the
intensity of a stimulus
that person can detect
WEBER’S LAW
• For any change in a
stimulus to be detected,
a constant proportion
of that stimulus must
be added or subtracted
• A.K.A.: Weber-Fechner
Law
SENSORY ADAPTATION
• Senses are tuned to
change
• Senses adapt to a
constant level of
stimulation
• Necessary to ignore
mundane
SIGNAL-DETECTION THEORY
• Def: the study of
people’s tendencies to
make correct judgments
in detecting the
presence of stimuli
• Radar operator
PROCESSING STIMULI
• Preattentive process:
extracting information
automatically
• Attentive process:
procedure that
considers only one part
of the stimuli presented
at a time
• Stroop Interference
Effect
SECTION 2: THE SENSES
VISION
• Most studied sense
• Pupil: opening in the iris
that regulates the amount
of light entering the eye
• Lens: flexible structure
that focuses light on the…
• Retina: innermost coating
of the back of the eye,
containing light sensitive
receptor cells
VISION CONTINUED
• Cones and Rods: light
receptors in the retina;
convert light energy
into neuronal impulses
• Cones: color
• Rods: night vision
• Optic Nerve: the nerve
that carries impulses
from the retina to the
brain
COLOR DEFICIENCY
• Affects 8% of American
men; <1% women
• Dysfunctional cones
• Red-green
• Yellow-blue
• Total deficiency: see in
black and white
BINOCULAR FUSION
• Def: 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
• Essential for depth
perception
NEARSIGHTEDNESS
• Eyeball is longer than
normal
• Objects focused at a
point in front of the
retina
• See objects that are
near, but not far
FARSIGHTEDNESS
• Eyeball is too short
• Objects focused slightly
behind the retina
• Distant objects are
clear, near objects are
not
HEARING
• Sound waves: vibrations
in the air
• Loudness determined
by amplitude (height) of
waves
• Strength determined by
decibels
• >110 decibels damages
hearing
HEARING
• Pitch depends on sound
wave frequency (rate of
vibration of medium
through which wave
travels)
PATH OF SOUND
• Outer ear (pinna) receives
waves
• Auditory canal vibrates
which vibrates the ear drum
• Middle ear: 3 tiny bones--hammer, anvil, and stirrup
• Inner ear: cochlea---liquid
moves, tiny hairs detect
motion, translate into
neuronal input and sent to
brain by the Auditory nerve
DEAFNESS
• 2 types:
• 1) Conduction deafness:
hindered physical motion
in the outer or middle ear
• Helped with conventional
hearing aid
• 2) Sensorineural deafness:
damage to the cochlea
• Helped with cochlear
implant
BALANCE
• Vestibular system: 3
semicircular canals that
provide the sense of
balance, located in the
inner ear and
connected to the brain
by a nerve
• Fluid in canals moves
• Hair cells translate
motion
SMELL
• Chemical sense
• Gaseous molecules
contact smell receptors
• Olfactory nerve: carries
smell impulses from the
nose to the brain
TASTE
•
•
•
•
•
•
•
5 primary tastes:
1) Sweet
2) Sour
3) Bitter
4) Salty
5) Umami (savory, meaty)
Combination of these
creates flavor
• Taste is more determined
by smell
SKIN SENSES
• Densely bundled nerve
endings create
sensitivity to pressure
• Some are sensitive to
hot and cold
• Pain results from many
different stimuli
PERCEPTIONS OF PAIN
• Sharp, localized pain
immediately after injury
• Dull, generalized pain
later
• Gate control theory of
pain: shifting attention
away from pain can
lessen its effects
BODY SENSES
• Kinesthesis: the sense
of movement and body
position
• Cooperates with
vestibular system and
vision
• Receptors in and near
muscles, tendons, and
joints
The way we interpret sensations and organize them into meaningful
experiences
SECTION 3: PERCEPTION
GESTALT
• Def: the experience that
comes from organizing
bits and pieces of info
into meaningful wholes
• Trying to identify
principles the brain uses
in building perception
GESTALT PRINCIPLES
•
•
•
•
•
•
1) Proximity
2) Continuity
3) Similarity
4) Simplicity
5) Closure
If elements are close to
one another or similar,
we perceive them as
one set
FIGURE-GROUND PERCEPTION
• The ability to
discriminate btwn a
figure and its
background
• Shows we can perceive
in more than one way
• Works with sound as
well
PERCEPTUAL INFERENCE
• Filling in the gaps in
what our senses tell us
• Largely automatic and
unconscious
• Depends on experience
LEARNING TO PERCEIVE
• Influenced by needs,
beliefs, and
expectations
• If we want something,
we’re more likely to see
it
• Perceptual set: twisting
truth to fit our own
belief system
SUBLIMINAL PERCEPTION
• Subliminal messages:
brief auditory or visual
messages that
presented below the
absolute threshold
• Not really effective
DEPTH PERCEPTION
MONOCULAR DEPTH CUES
• Can be used with a
single eye
• Relative height: objects
further away are higher
on your visual plane
• Interposition:
overlapping
• Light and shadows:
brightly lit objects are
closer
MORE MONOCULAR CUES
• Texture-density
gradient: close objects
have more detail
• Motion parallax: the
apparent movement of
stationary objects
relative to one another
that occurs when the
observer changes
position
MORE MONOCULAR CUES
• Linear perspective:
parallel lines converge
in the distance
• Relative motion: near
objects appear to move
in the opposite
direction that you do;
far objects seem to
travel with you
BINOCULAR DEPTH CUES
• Depend on movement
of both eyes
• Convergence: eyes turn
inward when looking at
nearby objects
• Retinal disparity
• Large disparity means
close; small means far
CONSTANCY
• Def: the tendency to
perceive certain objects
in the same way
regardless of changing
angle, distance, or
lighting
ILLUSIONS
• Def: perceptions that
misrepresent physical
stimuli
• Happens when
perceptual cues are
distorted so our brains
cannot correctly
interpret space, size,
and depth cues
EXTRASENSORY PERCEPTION
• Def: (ESP) an ability to gain
info by some means other
than the ordinary senses
• 4 types:
• 1) Clairvoyance: perceiving
w/o sensory input
• 2) Telepathy: mind reading
• 3) Psychokinesis: move
things with your mind
• 4) Precognition: foretell
events
I’m a big idiot
who likes to rob
people of their
money by
preying on their
personal loss