Transcript Sensation and Perception

Sensation and
Perception
Sensation
The
process of
taking in
information from
the environment
Perception
How
we recognize,
interpret, and
organize our
sensations
Input
comes from the
five senses:
Visual (Eyes)
Audio (Ears)
Cutaneous/Tactile
(Touch)
Olfaction (Smell) (Nose)
Gustation (Taste)
(Tongue)
Receptor Cells
Each
of the five senses
is specifically coded to
only take in one type of
stimulus, whether it be
light waves, sound
waves, smell, taste, or
touch.
Receptive Field
 The
area from which receptor
cells receive input (audio from
ears, visual from eyes, touch
from the skin, taste from the
tongue, smell from the nose)
Transduction
Changing
sensory input into
an electrochemical message,
from the sense receptors to
the brain, and the brain to the
correct area for action.
Contralateral Shift
When
information travels
from one side of the body
to the opposite side of the
brain for interpretation.
Kinesthetic Sense
 The
system for sensing the position
and movement of individual body
parts.
 Receptor cells located throughout
the muscles and joints of the body.
 A common disorientation of this
sense is a “phantom limb
sensation”
Phantom Limb Sensation
A
phantom limb is the
sensation that an
amputated or missing limb
is still attached to the body
and is moving
appropriately with other
body parts. But why?
Vestibular Sense
 The
system for sensing body orientation
and balance.
 Fluid in the semicircle canals of the
inner-ear maintain the body’s sense of
balance.
 A common disorientation of this sense is
when you spin around and around, then
stop. Your body has stopped moving,
but the fluid hasn’t.
Thresholds
Detection Threshold or
Absolute Threshold
The
minimum
intensity of energy
required to produce
sensation in a
receptor cell at least
50% of the time
 Taste:
1 gram of table salt in 500 liters of
water
 Smell: 1 drop of perfume diffused
throughout a three room apartment
 Touch: The wing of a bee falling on your
cheek from a height of 1 centimeter
 Hearing: The tick of a watch from 6 meters
away
 Vision: A candle flame on a clear night, 30
miles away
Difference Threshold or
Just Noticeable Difference
The
smallest
change in
stimulation that
you can detect
Ernst Weber and
Weber’s Law
 The
greater the magnitude of the
stimulus, the larger the difference
must be in order to be noticed
 IE.
If you are carrying 20 lbs. and
add 5 lbs., it’s noticeable. If you are
carrying 100 pounds and add 5
pounds, it may not be noticeable.
You may need to add 20 lbs. to 100
pounds to make it noticeable.
Sensory Adaptation
 Diminished
sensitivity as a result of
constant and unchanging stimulation.
 You jump into a swimming pool of
cold water, but eventually you “get
used to it”. Or, you wear your
glasses so often that you sometimes
forget that they are on.
Selective Attention
 Focusing
conscious awareness on a
particular stimulus while excluding
others.
 With so much stimulus bombarding our
senses every second, we can’t respond
to everything, all of the time. Listening
to this lecture, you have chosen to
ignore the feel of your shirt on your
skin, ignored the sound of the heater,
ignored the temperature of the room.
IE.
It is estimated that our
combined five senses take
in over 11 million bits of
information every second,
of which we consciously
process about 40.
Cocktail-Party
Phenomenon
 Describes
instances when your
attention will involuntarily switch when
you hear or see something familiar.
 IE.
You are at a party, paying close
attention to a conversation with a
young lady. Someone in a separate
conversation across the room says the
name “Chris”. Without thinking about
it, you hear the name and are
momentarily distracted.
Subliminal Perception
 Thresholds
imply that there must
be stimulus below and beyond
our current levels of detection.
Can human behavior be
influenced by stimulus that is
below or beyond our level of
awareness?
Subliminal Perception
Extrasensory Perception
 Some
people claim to have extra
powers of perception, or the
ability to respond to an unknown
event that is not presented to any
of the known senses.
 Parapsychology
Examples of
Extrasensory Perception
Telepathy: Transfer of information on
thoughts or feelings between individuals by
means other than the five classical senses
 Precognition: Perception of information
about future places or events before they
occur.
 Clairvoyance: Obtaining information about
places or events at remote locations, by
means unknown to current science.

Clairvoyance and Precognition?
The telephone rings and you know who it is.
You know what someone is about to say to you
before they say the words.
You get a hunch or knowing about something and
it turns out to be correct.
You get a sudden urge to go somewhere or do
something, and when you do that thing, and it
turns out to be the right thing that you should
have done. And you are pleased.
You get a sudden urge to go somewhere or do
something, and you ignore it or don't do it, and it
turns out that you should have. And you regret it.
You can understand someone's true inner feelings
even though on the outside they are hiding them.
You have a feeling that there is a presence or that
someone or something behind the scene is
helping you.
When something happens in your life, either good
or not so good, and you suddenly understand a
higher purpose behind it.
You sometimes hear a soft inner voice tipping you
off about things happening in your life or in the
life of someone else.
Visual Sensation
Human Eyeball
Cornea
 transparent
protective coating over
the front part of the eye
Iris
colored part of the eye – this muscle
dilates or contracts the pupil to allow
more or less light to enter
 the
Pupil
the
small, adjustable
center of the iris that
allows light to enter the
eye
Lens

flexible enough to focus on objects near or far
(accommodation) – if an object is very close
is gets smaller and rounder; if an object is
further away, it get larger and wider
Retina
lining of the back of the eyeball –
the lens focuses an image from the
outside world on the retina
 inner
Fovea
 On
the retina, directly behind the lens.
The area of sharpest picture.
– the sharpness of vision
 Nearsightedness – the misshapen
eyeball focuses light rays in front of the
retina – you will see near objects well,
but not far away objects
 Farsightedness – the light rays from
nearby objects reach the retina before
they have been focused – you will see
far objects better than near objects
 Acuity
Rods and Cones
 In
the retina. Rods determine shades of
light and dark. Cones determine color.
About 130 million total.
Optic Nerve

Takes the visual information from the eye and
sends it to the brain for processing. Different
parts of the brain interpret what the shapes,
colors, motion, depth, etc. we see are, and tell
us what it is, and what to do with it.
Blind Spot

the area closest to the optic nerve, that has
no receptor cells
Optic Chiasm
 the
point in the brain at which
messages from the visual fields are
split to the appropriate areas of the
brain
 Prosopagonosia - stroke victim
disorder in which victims cannot
recognize faces, but can still see
well and recognize emotions on
faces
Stereopsis (Contralateral
Shift)
Color Vision
There
are two theories of
color vision:
Trichromatic
Theory
Opponent-Process Theory
Young-Helmholtz Theory
Trichromatic Theory
Rods
and cones are pre-set
to be sensitive to RED,
GREEN, and BLUE. All of
the colors that we see are
combinations of those three
colors.
Opponent-Process Theory
Sensory
receptors in
the retina come in
pairs:
Red/Green
Yellow/Blue
Black/White
Opponent-Process Theory
If one sensor is stimulated, the other is
inhibited
 If one sensor is over-stimulated, and fatigues,
the paired sensor will be activated, causing
an afterimage
 If a person is missing a particular pair of
sensors, they will be colorblind to those hues


Dichromatic Color Blindness have difficulty
seeing shades of red and green, or yellow
and blue
Color
– the different colors that we
see and the name given to a
color
 Saturation – the richness or
vividness of a color
 Brightness – how close a color is
to white or black
 Hue
– determined by the wavelength
(the distance from one wave peak to the
next) of the light wave that the eye is
receiving
 Hue
 Brightness
is influenced by the
height of the waves (amplitude) of
light that are received by the eye
 The
shorter the wavelength, more
bluish colors
 The longer the wavelength, more
reddish colors
 The higher the wave, more
yellowish
 The lower the wave, more
greenish