Transcript Sensation and Perception

Review Session 3
 Sensation- activation of our
 Perception- understanding
sensations
 Transduction- information
received by our sensory
organs is transformed into
neural impulses
 Travel
senses
these
through the thalamus (except
for smell) to different areas of the
brain
 Sensory
adaptationdecreasing responsiveness
to a stimuli due to constant
stimulation
 Sensory habituation- our
perception is partially due to
how focused we are on them
 Cocktail party phenomenonwhen someone says our name
across a room, we will switch our
attention involuntarily
7 Senses
Energy
Senses
Sight
Sound
Chemical
Senses
Touch
Taste
Smell
Body
Position
Balance
Kinesthesis
Vestibular
 Step
1- Gathering Light Light is reflected off objects
and gathered by the eye.
• Visual light is only a small part
of the electromagnetic spectrum;
color we perceive depends on:
 Wavelength- determines the hue we
see
 Amplitude- determines the
brightness of the color
• Objects appear a color because
they reflect that color of light.
 Step
2: Within the Eye- Light coming
from an object enters the eye
• First goes through the cornea, a protective
covering that also helps focus
• Then goes through the pupil which opens
(dilates) to let light in. The iris (muscles)
controls this opening
• Through the process of accommodation, light is
focused by the lens and the image is flipped
upside down and inverted
• The focused image projects on the retina at the
back of the eye
 Step
3: Transduction- the translation of
stimuli into neural signals, specifically when
light activates neurons in the retina
• 1st Layer- directly activated by light
 Cones- respond to color, concentrated in the fovea
(center of the retina)
 Rods- outnumber cones, respond to black and
white, reason for peripheral vision
• 2nd Layer- activated by rods and cones
firing
 Ganglion cells- their axons make up
the optic nerve- thalamus- occipital
lobe (visual cortex)
 Step
4- In the Brain
• Visual cortex in the brain receives the impulses
from the retina
• Impulses activate feature detectors- specific
groups of neurons that respond to different types
of visual images (vertical lines, curves, motion,
etc.)
Cell’s
responses
Stimulus

Trichromatic Theory- we have three types of
cones in the retina that detect the colors blue,
red, and green.
• These cones are activated in different combinations to
produce all colors of the visual spectrum.
• Can’t explain afterimages or color blindness

Opponent-Process Theory- sensory receptors
arranges in the retina come in pairs: red/green
pairs, yellow/blue pairs, and black/white pairs.
• If one sensor is stimulated, its pair is inhibited from firing.
If you stare at the color red for awhile, you fatigue the
sensors for red.
• People with color blindness are missing one pair

Most researchers agree in a combination of both
 Sounds
create vibrating sound waves that
are collected by our ears
 Vibrations go through transduction and
neural impulses are sent to the brain
 Amplitude-
height
the
of the wave,
determines the loudness of a sound,
measured in decibels
 Frequency- the l---e----n----g----t----h of the
wave, determines pitch, measured in
megahertz
Sound waves are collected in the outer ear or pinna
The waves travel down the ear canal until they reach the ear drum
(timpanic membrane)
The eardrum vibrates the hammer, anvil, and stirrup (the ossicles)
The vibration of the bones causes the vibration of the oval window
The oval window vibrates the fluid in the cochlea, which causes the
hair cells inside to vibrate
The Organ of Corti neurons are activated and fire, transferring
impulses to the brain via the auditory nerve
 How
do we hear different tones?
Place
Theory
The hair cells in the
cochlea respond to
different frequencies of
sound based on where
they are located some
respond to high pitches
and some to low; we
hear pitch b/c hair cells
move in different
places. Accurately
describes high tones
Frequency
Theory
We sense pitch
because hair
cells fire at
different rates
(frequencies)
in the cochlea.
Accurately
describes low
tones.
 Conduction
Hearing Loss
• hearing loss caused by damage to the
mechanical system that conducts sound waves to
the cochlea
 Nerve
Hearing Loss
• hearing loss caused by damage to the cochlea’s
receptor cells or to the auditory nerve, usually
by loud noise, more difficult to treat
 Exact
relationship between nerve
endings is not understood
 Skin Sensations
• Pressure
 only skin sensation with identifiable receptors
• Warmth
• Cold
• Pain
 Gate Control Theory
• Some pain messages have higher priority than
others
• When a higher priority message is sent, the
“gate” swings open for it and swings shut for a
low priority message
• Scratching an itch: the gate swings open
for high intensity chemicals
• Endorphins (inside morphine in the
brain) control pain and can also
swing the gate shut
 Chemicals
from the food we eat are
absorbed by taste buds on the tongue,
located on the papillae (bumps on tongue)
• Also located on some parts of the cheek and roof of
the mouth
 Four
tastes: sweet,
salty, sour, and bitter
 People differ: more
densely packed taste
buds, more intense taste
 Flavor: taste + smell
Molecules of substances rise into the air , are
drawn into the nose, and settle into the mucus
membranes at the top of each nostril and are
absorbed by receptor cells- as many as 100
different types exist
 Linked to the olfactory bulb,
which gathers and send the
information to the brain
 Connects at the amygdala
and then to the hippocampus
instead of through the
thalamus

 Sense
of how our body is oriented in
space
 Three semicircular canals in the ear are
filled with liquid; when the position of
your head changes, sensors in the canals
move
 Nausea and dizziness- agitated
canals
 Gives
feedback about the orientation and
position of specific body parts
 Receptors in the muscles and joints send
info that combined with
visual feedback, lets us keep
track of our body
 Absolute
threshold- the smallest amount
of a stimulus that we can detect 50% of
the time
• Ex) candle flame 30 miles away on a dark
night, one drop of perfume in a three room
house, etc.
 Subliminal-
threshold
stimuli below our absolute
• No scientific evidence that it can change
behavior
 Difference
threshold (just noticeable
difference- JND)- the smallest amount of
change needed in a stimulus before we can
notice a change
 Weber’s Law- the change needed is
proportional to the original intensity of the
stimulus
 The more intense the stimulus, the more it
will need to change before we detect a
change
 Investigates
the effects of the distractions
and interference we experience while
perceiving the world
• What will we perceive among competing stimuli
• Take motivation and
expectations into accountresponse criteria
• False positive- when we think
we perceive a stimulus that is
not there
• False negative- not perceiving a
stimulus that is present
 We
perceive by filling in the gaps in what
we sense by using background
knowledge
• Schemata- mental representations on
how we expect the world to be
• Perceptual set- a predisposition to
perceive the world in a certain way
 Backmasking- music
 Aka
Feature Analysis- using the features
of the object itself to create a complete
perception
• Happens very automatically
• Takes longer than top-down but is more accurate
 Figure
and Ground- organization of the
visual field into objects
(figures) that stand out
from their
surroundings (ground)
 We
normally perceive images as groups,
not isolated elements
 Ability
to maintain a constant perception
of an object despite changes
• Size constancy
• Shape constancy
• Brightness constancy
 Sometimes
out brains perceive objects to
be moving when they are not
• Stroboscopic effect (movies, flip books)- images
in a series of pictures presented at a certain
speed
• Phi phenomenon- series of light bulbs turned on
and off at a particular rate
• Autokinetic effect- a spot of light is projected
steadily onto the same place of a wall in a dark
room
 Depend
on experience- crawling- Visual
Cliff Experiment (Eleanor Gibson)
 Monocular
Cues
• relative size
 smaller image is more distant
• interposition
 closer object blocks distant object
• relative clarity
 hazy object seen as more distant
• texture
coarse --> close
fine --> distant
 Binocular
cues
• retinal disparity
 images from the two eyes differ
 closer the object, the larger the disparity
• convergence
 neuromuscular cue
 two eyes move inward for near objects


1) Which of the following is NOT an example of a monocular visual depth
perception cue?
• Texture gradient
• Motion parallax
• Interposition
• Opponent process
• Relative size
2) The cochlea is responsible for
• Protecting the surface of the eye
• Transmitting vibrations received by the eardrum to the hammer, anvil,
and stirrup
• Transforming vibrations into neural signals
• Coordinating impulses from the rods and cones in the retina
• Sending messages to the brain about orientation of the head and body


3) In a perception research lab, you are asked to describe the shape of the top
of a box as the box is slowly rotated. What concept are the researchers most
likely investigating?
• feature detectors in the retina
• Feature detectors in the occipital lobe
• Placement of rods and cones in the retina
• Binocular depth cues
• Shape constancy
4) The blind spot in our eye results from
• The lack of receptors at the spot where the optic nerve connects to the
retina
• The shadow the pupil makes on the retina
• Competing processing between the visual cortices in the left and right
hemispheres
• Floating debris in the space between the lens and the retina
• Retinal damage from bright light


5) Smell and taste are called _______ because _______.
• Energy senses; they send impulses to the brain in the form of electric
energy
• Chemical senses; they detect chemicals in what we taste and smell
• Flavors senses; smell and taste combine to create flavor
• Chemical senses; they send impulses to the brain in the form of
chemicals
• Memory senses; they both have powerful connections to memory
6) Weber’s law determines
• Absolute threshold
• Focal length of the eye
• Level of subliminal messages
• Amplitude of sound waves
• Just-noticeable difference


7)Color blindness and color afterimages are best explained by what
theory of color vision?
• Trichromatic theory
• Visible hue theory
• Opponent-process theory
• Dichromatic theory
• Binocular disparity theory
8) You are shown a picture of your grandfather's face, but the eyes and
mouth are blocked our. You still recognize it as a picture of your
grandfather. What type of processing best explains this example of
perception?
• Bottom-up processing
• Signal detection theory
• Top-down processing
• Opponent-process theory
• Gestalt replacement theory