Transcript PPT Notes: Sensation & Perception

Sensation & Perception
Sensation is your window to the world!
Perception is interpreting what comes
in your window!
Sensation
Stimulation of
sensory receptors
and the transmission
of sensory
information to the
central nervous
system (spinal cord
& brain)
Perception
Psychological
process through
which we select,
organize and
interpret our
sensations
Bottom Up Processing
Analysis that begins with the sense
receptors and works up to the brain’s
integration of sensory information
Top Down Processing
Information processing guided by higher
level mental processes; as when we
construct perceptions drawing on our
experience and expectations
Bottom-Up Processing
• Also called feature
analysis.
• We use the features
on the object itself to
build a perception.
• Takes longer that topdown but is more
accurate.
• Our brain instantly
tries to put together a
visual image using cues
from our environment
You’ll know that the
shape coming toward
you is a human being
before you’ll detect the
color of her hair or eyes
or even her gender.
Top-Down Processing
• We perceive by filling
the gaps in what we
sense.
• I _ant ch_co_ate ic_
cr_am.
• Based on our
experiences and
schemas.
• If you see many old men
in glasses, you are more
apt to process a picture
of an old man (even when
you may be in error).
Psychophysics
Study of the relationship between
physical characteristics of stimuli and
our psychological experience of them
Light  brightness
Sound  volume
Pressure  Weight
Taste  Sweetness
Weber’s Law
• Computes the Just
Noticeable Difference.
• The change needed is
proportional to the
original intensity of the
stimulus.
• The more intense the
stimulus the more
change is needed to
notice the difference.
• 8% for vision.
Absolute Threshold
• The smallest amount
of a stimuli we can
detect about half of
the time.
(Just Notable Difference)
Difference Threshold
The smallest amount of change needed to detect in a stimulus before we detect a
change.
Signal Detection theory
• Absolute thresholds
are not really
absolute.
• Things like motivation
or physical state can
effect what we
sense.
• False Positives
• False Negatives
My wife could sleep through a war, but if
one of our sons even whimpers, she is up!!!
Sensory Adaptation
• Decreased
responsiveness to
stimuli due to
constant stimulation.
Do you feel your underwear all day?
Subliminal Stimulation
Hungry? Eat Popcorn and Drink Coca-Cola
Do movies have subliminal messages (“below
threshold”) we can unconsciously sense?
And without our awareness they have
extraordinary suggestive powers?
Most likely is a hoax, but thinking it may be
in the movie leads to a placebo effect, which
is what is actually making us hungry and
thirsty.
Believing in the subliminal message makes us
thirsty!
Vision
• Our most dominating
sense.
• Visual Capture
Transduction
• Transforming signals
into neural impulses.
• Information goes
from the senses to
the thalamus , then
to the various areas
in the brain.
Remember Ethan in Sky High. He
changes his body to slime. Solid
form to liquid form. Change from
one form of energy to another.
Click the picture to watch power
placement.
Phase One: Gathering Light
•
•
•
•
•
The height of a wave gives us it’s intensity (brightness).
The length of the wave gives us it’s hue (color).
ROY G BIV
The longer the wave the more red.
The shorter the wavelength the more violet.
Getting the light in the eye
Light enters through the cornea!
Hearing
Our auditory sense
We hear sound WAVES
• The height of the wave gives us the amplitude of the
sound.
• The frequency of the wave gives us the pitch if the sound.
The Ear
Transduction in the ear
• Sound waves hit the eardrum
then anvil then hammer then
stirrup then oval window.
• Everything is just vibrating.
• Then the cochlea vibrates.
• The cochlea is lined with mucus
called basilar membrane.
• In basilar membrane there are
hair cells.
• When hair cells vibrate they
turn vibrations into neural
impulses which are called organ
of Corti.
• Sent then to thalamus up
auditory nerve.
It is all about the vibrations!!!
How do we locate sounds?
Sound waves strike one ear sooner and more
intensely than the other from this
information, our brains compute the sounds
location
Pitch Theories
Place Theory and Frequency Theory
Place Theory
• Different hairs
vibrate in the
cochlea when they
different pitches.
• So some hairs
vibrate when they
hear high and other
vibrate when they
hear low pitches.
Frequency Theory
• All the hairs vibrate
but at different
speeds.
Deafness
Conduction Deafness
• Something goes wrong
with the sound and the
vibration on the way to
the cochlea.
• You can replace the
bones or get a hearing
aid to help.
Nerve (sensorineural)
Deafness
• The hair cells in the cochlea
get damaged.
• Loud noises can cause this
type of deafness.
• NO WAY to replace the hairs.
• Cochlea implant is possible.
Touch
• Receptors located in
our skin.
• Gate Control Theory
of Pain
Taste
• We have bumps on
our tongue called
papillae.
• Taste buds are
located on the
papillae (they are
actually all over the
mouth).
• Sweet, salty, sour
and bitter, and
umami (meat).
Vestibular Sense
• Tells us where our
body is oriented in
space.
• Our sense of
balance.
• Located in our
semicircular canals
in our ears.
Kinesthetic Sense
• Tells us where our
body parts are.
• Receptors located in
our muscles and
joints.
Without the kinesthetic sense
you could touch the button to
make copies of your buttocks.
Perception
The process of organizing and interpreting
information, enabling us to recognize
meaningful objects and events.
Illusions help us understand
perception!
• Understanding illusions requires an
understanding of how we transform
sensations into meaningful perceptions
– Size & distance
– Principles of relative height
– Grouping
Selective Attention
 Selective Attention
 Focusing of conscious awareness on a
particular stimulus
 Cocktail Party Effect (listen to one voice,
among many)
Change Blindness
• An example of our lack of awareness of things
going on around us… Change Blindness!
• Change Blindness: after a brief visual
interruption, we fail to notice a change in the
environment
• (Change Blindness Video)
• Visual Capture: tendency of vision to
dominate the other senses
Absolute Threshold
• The smallest amount
of a stimuli we can
detect about half of
the time.
(Just Notable Difference)
Difference Threshold
The smallest amount of change needed to detect in a stimulus before we
detect a change.
Weber’s Law
• Computes the Just
Noticeable Difference.
• The change needed is
proportional to the
original intensity of the
stimulus.
• The more intense the
stimulus the more
change is needed to
notice the difference.
• 8% for vision.
Perceptual Ideas
Signal Detection theory
• Absolute thresholds
are not really
absolute.
• Things like motivation
or physical state can
effect what we
sense.
• False Positives
• False Negatives
My wife could sleep through a war, but if
one of our sons even whimpers, she is up!!!
Top-Down Processing
• We perceive by filling
the gaps in what we
sense.
• I _ant ch_co_ate ic_
cr_am.
• Based on our
experiences and
schemas.
• If you see many old men
in glasses, you are more
apt to process a picture
of an old man (even when
you may be in error).
Bottom-Up Processing
• Also called feature
analysis.
• We use the features
on the object itself
to build a
perception.
• Takes longer that
top-down but is more
accurate.
Click to see an example
of bottom –up
processing.
Gestalt Psychology
• We organize sensations into meaningful wholes
(gestalts), that may exceed the sum of their parts and
be regrouped into more than one perception
• Figure-Ground Relationships- to recognize an object,
we must first perceive it as a figure against its
surrounding stimuli (ground)
– Reversible… a single stimuli can trigger more than one
perception!
Figure Ground Relationship
Our first perceptual
decision is what is the
image is the figure and
what is the background.
Gestalt Psychology
• Gestalt psychologists focused on
how we GROUP objects together.
• We innately look at things in groups
and not as isolated elements.
• Proximity (group objects that are
close together as being part of
same group)
• Similarity (objects similar in
appearance are perceived as being
part of same group)
• Continuity (objects that form a
continuous form are perceived as
same group)
• Closure (like top-down
processing…we fill gaps in if we can
recognize it)
Constancy
• Tendency to see
objects as unchanging
while the stimuli from
them change in size,
shape, and lightness
• Shape Constancy
• Size Constancy
• Brightness Constancy
– Relative luminance: the
amount of light an
object reflects relative
to its surroundings
Depth Perception
• Our ability to see objects in 3D despite their 2D
representations on our retinas
Monocular Cues
• You really only need
one eye to use these
(used in art classes to
show depth).
• Linear Perspective
• Interposition
• Relative size
• Texture gradient
• Shadowing
Perceived Motion
• Stroboscopic effect
(flip book effect)
• Phi phenomenon
• Autokinetic Effect
(if people stare at a
white spotlight in a
dark room, it
appears to move.)
Binocular Cues
• We need both of our
eyes to use these cues.
• Retinal Disparity (as an
object comes closer to
us, the differences in
images between our
eyes becomes greater.
• Convergence (as an
object comes closer our
eyes have to come
together to keep
focused on the object).
Depth Cues
• Eleanor Gibson and her
Visual Cliff Experiment.
• If you are old enough to
crawl, you are old enough
to see depth perception.
• We see depth by using
two cues that researchers
have put in two
categories:
• Monocular Cues
• Binocular Cues
3-D Movies
• Simulate retinal disparity
• Use 2 cameras to photograph each scene
• Special glasses allow each eye to see only the image
from one camera
• Each eye focuses = brain perceives one 3D image!
• Perceptions are the constructs of our brains!
Moon Illusion
• Size and distance cues
at the horizon make the
moon seem further
away when high in the
night sky
• Moon closer to horizon
will seem larger