Sensation

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Sensation

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Title: Sensation

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Sensation Perception
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The Forest Has Eyes Bev Doolittle
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I. General Characteristics of Sensation

A. Basic Definitions
1. Sensation the process by which our sensory
receptors and nervous system receive and
represent stimulus energies from our environment
2. Perception The process of organizing and
interpreting sensory information, enabling us to
recognize meaningful objects and events

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Processing

3. Bottom-up-processing analysis that begins
with the sense receptors and works up to the
brains integration of sensory information
AKA Sensory Anaylsis
4. Top-down-processing information processing
guided by higher level mental processes as when
we construct perceptions drawing on our
experience and expectations.
AKA Interpretation of what our senses detect

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The Forest Has Eyes Bev Doolittle
Bottom Up- sensory systems detect the lines,
angles and colors that form the horses, rider and
surroundings. Top-Down- consider the
paintings title, we notice the hidden
expressions, and direct our attention to those
aspects.
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B. An example of Top-Down Processing

1. E.H. is a patient who can see individual
features of a face, but cannot see the face as a
whole.
Shown a familiar face her autonomic nervous
system will respond but she will be unable to
identify the face.

2. Her problem was top down because the
information was correctly being sent by the eyes.
The brain however was not processing the
information properly.
3. Prosopagnosia complete sensation without
complete perception

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Selective Attention

The focusing of conscious awareness on a
particular stimulus.
Your five senses take in 11 million bits of info
per second
You consciously process about 40
Unconsciously your mind makes use of the other
million upon million bits
You dont realize but your nose is in your line
of vision.
SELECTIVE ATTENTION TEST

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Inattentional Blindness

Failing to see visible objects when out attention
is directed elsewhere.
At the level of conscious awareness, we are
blind to all but a tiny fraction of stuff
occurring in front of us.

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Change Blindness

Failing to notice changes in the environment.
A form of inattentional blindness.

In this experiment a man asks for directions from
the older gentleman. During the process two
construction workers walk in between the two.
During this process the man asking for directions
is switched with another man. Our selective
attention (focusing on giving directions)
distracts from the details of the scene.

Mindfulness - our awareness of and attention to
what is taking place.
Brown Ryan Mindful Attention Awareness Scale

Range 15-90
Higher scores reflect greater mindfulness or
greater attention to and awareness of current
experiences.
People with higher scores tend to be more
observant of what is occuring both internally
externally.
Average Score 55.8

1. Psychophysics the study of relationships
between the physical characteristics of stimuli,
such as their intensity, and our psychological
experience of them

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Sensing the World
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Absolute Threshold
a. Absolute threshold the minimum stimulation
needed to detect a particular stimulus 50 of the
time
the absolute threshold varies among individuals

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Signal detection
a. predicts how and when we detect the presence
of a faint stimulus amid background stimulation
b. Assumes that there is no single absolute
threshold and that detection depends partly on a
persons experience, expectations, motivation and
level of fatigue
Subliminal Stimulation
a. We can sense stimuli below our threshold
b. The controversy first arose over a claim that
movie theatres were inserting subliminal messages
into their movies
c. Much of our information processing occurs
automatically, out of sight, off the radar screen
of our conscious mind.

b. Operates on two assumptions
that we can sense stimuli below the threshold
without our awareness these stimuli have
extraordinary suggestive powers
c. Subliminal below ones absolute threshold
for conscious awareness

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d. Studies supporting subliminal perception
Krosnick Others 1992 flashed either a bad
image or good image before showing a persons
face - the bad image created a bad image of the
persons face
Murphy Zajonc similar study using Chinese
characters found similar results
e. Studies disproving subliminal perception
The Canadian Brodcasting Corp. participated in a
study that flashed a message 352 times during a
TV show. Then asked people to call in and guess
the message. None did. The message was
Telephone Now! - there was no increase in phone
usage after the messages

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Difference Threshold

a. Difference threshold (aka Just-noticeable-diff
erence) the minimum difference that a person
can detect between two stimuli
b. First studied by Ernst Heinrich Weber
c. Webers Law the principle that, to perceive
their difference, two stimuli must differ by a
constant minimum percentage

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Sensory Adaptation

1. Sensory adaptation diminished sensitivity
as a consequence of constant stimulation
After constant exposure to a stimulus, our nerve
cells fire less frequently
2. For example
a. We often stop noticing our own cologne or
perfume
b. We ignore the repetitive noises around us
c. We ignore the feeling of glasses on our face
So if we stare at a point long enough, what would
happen? Would sensory adaptation occur and the
point disappear?

Get out a piece of white paper!

Stare directly at the center for 1 minute!

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Stare directly at the center dot for 1 minute!

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Have Fun!

http//www.illusions.org/

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VISION

How does our body construct our conscious visual
experience? How do we transform particles of
light energy into colorful sights?

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Vision

A. Stimulus Input
1. Transduction
a. conversion of one form of energy into another
b. In sensation, the transforming of stimulus
energies into neural impulses
2. The three psychological properties of light
a. Wavelength the distance from the peak of
one light or sound wave to the peak of the next

b. Hue the dimension of color that is
determined by the wavelength of light
long wave lengths reddish colors
short wave lengths bluish colors
c. Amplitude the height of a wave measured
from the trough to the peak
d. Intensity the amount of energy in a light
or sound wave which we measure as brightness or
loudness
great amplitude bright colors loud sounds
low amplitude dull colors soft sounds
e. Saturation how pure the light or sound is,
for example reddish-orange and blue-green are
less pure

B. The Human Eye
1. The parts of the eye
a. Cornea a transparent protector covering the
eye
b. Iris
a ring of muscle tissue that forms the colored
portion of the eye around the pupil
and controls the size of the pupil opening
c. Pupil the adjustable opening in the center
of the eye through which light enters
d. Lens the transparent structure behind the
pupil that changes shape to focus images on the
retina

2. Basic Visual Processes
a. Accommodation the process by which the
eyes lens changes shape to focus the image of
near objects on the retina
b. The Retina
the light sensitive inner surface of the eye,
containing the receptor rods and cones plus
layers of neurons that begin the processing of
visual information.
c. Fovea the central focal point in the
retina, around which the eyes cones cluster

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d. Nearsightedness a condition in which nearby
objects are seen more clearly than distant
objects because the lens focuses the image of
distant objects in front of the retina

e. Farsightedness a condition in which faraway
objects are seen more clearly than near objects
because the image of near objects is focused
behind the retina

3. The retina
a. Rods
retinal receptors that detect black, white, and
gray
necessary for peripheral and twilight vision,
when cones do not respond
b. Cones
receptor cells that are concentrated near the
center of the retina and that function in
daylight or in well-lit conditions
the cones detect fine detail and give rise to
color sensations

Remember This
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c. The pathway of light enters through the
pupil, lens focuses it on retina
Light strikes the rods and cones at the back of
the retina then moves forward to the bipolar
cells and the ganglion cells.
The ganglion cells formed the optic nerve which
carries info to the thalamus.
The optic nerve can send nearly 1 million
messages at once.

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d. The blind spot the point at which the optic
nerve leaves the eye, creating a blind spot
because no receptor cells are located there

C. Feature Detection- nerve cells in the brain
that respond to specific features of the
stimulus, such as shape, angle or movement.
Detectors in the visual cortex pass info to other
areas of the brain in order to response.
Ex Face Recognition occurs in the temporal lobe
just behind the right ear.

D. Visual Processing Parallel processing
1. Parallel processing
a. The processing of several aspects of a
problem simultaneously
b. The brains natural mode of information
processing for many functions, including vision
The brain divides a visual scene into sub
dimensions such as color, movement, form, and
depth. We then construct our perceptions by
integrating the separate but parallel work of the
different visual teams.

2. Examples
a. Blindsight the ability to respond to
something not consciously perceived
b. Visual agnosia an inability to recognize
objects despite otherwise satisfactory vision.
c. Prosopagnosia ability to recognize objects
but not faces

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What percentage of the electromagnetic spectrum
can humans see?
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E. Visual Information Processing Color Vision
1. Subtractive and additive color mixing
a. Subtractive color mixing is the process we
are familiar with in which we mix blue and yellow
and get green. It is subtractive because you are
subtracting the number of wavelengths that are
reflected

b. Additive color mixing is the process of
mixing wavelengths of light
The primary colors are therefore Red, Green and
Blue
It was from this information that the first
theories of color vision were developed.

2. Young-Helmoltz/Trichromatic Theory
a. The theory that the retina contains three
different color receptors
b. One most sensitive to red, one to green, one
to blue
c. Which when stimulated in combination can
produce the perception of any color

d. Color blindness not actually blind but they
lack the proper receptors for red or green
Lack of functioning cones
e. Problems with the theory
Why is it that people who are color blind for red
are also color blind for green. Yet they see
yellow fine which is produced by combining red
wavelengths with green wavelengths
After images when you stare at a green square
for a while and look at a white sheet of paper
you see red, greens opponent color.

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3. The Hering Opponent Process Theory
a. The theory that opposing retinal process
(red-green, yellow- blue, white - black) enable
color vision
b. For example, some cells are stimulated by
green and inhibited by red others are stimulated
by red and inhibited by green
c. Color Constancy a problem for the Opponent
Process Theory
perceiving familiar objects as having consistent
color, even if changing illumination alters the
wavelengths reflected by the object

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If you put on green tinted glasses you still see
objects as the correct color. Your brain
subtracts the green from the object and sees the
true color
4. The Retinex Theory
a. A combination of the words retina and cortex
b. When information from various parts of the
retina reaches the cortex, the cortex compares
the inputs to determine the brightness and color
perception for each area

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c. Feature Detectors nerve cells in the brain
that respond to specific features of the
stimulus, such as shape, angle or movement
Hubel and Wiesel found that various receptor
cells respond maximally to a bar flashed at a
particular angle.
They identified three different types of cells in
the visual cortex, Simple Cells, Complex
cells,and hyper complex or End-stopped cells

C. Visual Information Processing Feature
Detection
1. Some basic terms
a. Visual Field the whole area of the world
that you can see at any time. Divided into left
and right visual fields
b. Receptive Field the part of the visual
field to which any one neuron responds

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The Auditory Sense
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How do we hear?

Draw a bow across a violin and the resulting
stimulus energy is sound waves- molecules of air,
each bumping into the next. Our ears detect these
brief air pressure changes. The ears then
transforms the vibrating air into nerve impulses,
which our brain decodes as sound.

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Sound

A. The Auditory Stimulus
1. Audition the sense of hearing
2. Sound is caused by vibrations of air
molecules
3. Three psychological properties of sound
a. Frequency the number of complete
wavelengths that pass a point in a given time
b. Pitch a tones highness or lowness depends
on frequency
c. Loudness is determined by the amplitude of
the sound wave. Loudness is measured in
decibels.

B. The Human Ear and Transduction
1. The outer ear- channels sound waves through
the auditory canal to the eardrum.
Eardrum- tight membrane that vibrates with waves

2. The middle ear the chamber between the
eardrum and cochlea containing three tiny bones
(hammer, anvil, stirrup) that concentrate the
vibrations of the eardrum on the cochleas oval
window

3. Inner ear the innermost part of the ear
containing the cochlea, basilar membrane and hair
cells.
a. The cochlea a coiled, bony fluid- filled
tube in the inner ear through which sound waves
trigger nerve impulses
b. The basilar membrane a membrane inside the
cochlea that is lined with hair cells
c. The hair cells (around 16,000) vibrate
sending a signal to the auditory nerve

Incoming vibrations cause the cochleas membrane
(oval window) to vibrate, jostling the fluid that
fills the cochlea tube.

While the tube fills with fluid, this motion
causes ripples in the basilar membrane, bending
hair cells lining its surface.
Hair cell movement triggers impulses in the
adjacent nerve cells, whose axons converge to
form the auditory nerve
This sends neural messages to the thalamus then
to the temporal lobe for
processing.

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C. Theories of Hearing
1. Loudness is perceived by the number of hair
cells that respond
2. Pitch
a. The Place theory in hearing, the
theory that links the pitch we hear with
the place where the cochleas
membrane is stimulated
explains how we hear high pitched sounds
but fails to show how we hear low pitched sounds

b. The frequency theory in hearing, the theory
that the rate of nerve impulses traveling up the
auditory nerve matches the frequency of a tone,
thus enabling us to sense its pitch
explains how we hear low pitched sounds
but fails to explain how we hear high pitched
sounds
c. Most likely a combination of the two combines
to explain how we hear different pitches

d. The Volley Principle shows how when hair
cells fire in alternating patterns we can hear
sounds that have frequencies above 1000 times per
second
3. Determining the location of a sound
a. Having two ears allows us to locate the
source of a sound
b. Our auditory system is extremely sensitive to
how intense and when a sound arrives

D. Hearing Loss
1. Conduction deafness hearing loss caused by
damage to the mechanical system that conducts
sound waves to the cochlea
2. Sensorineural or nerve deafness hearing
loss caused by damage to the cochleas receptor
cells or to the auditory nerves
3. Deaf advocates disagree with the use of
cochlear implants for children born deaf. They
reason that deafness is NOT a disability.

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Hearing through bone conduction

When you plug your ears and listen to yourself
speak, you hear both the sound conducted by air
waves to the outer ear and that carried directly
to the auditory nerve by bone conduction.
Bone conduction demonstration.

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Hearing through bone conduction

People who are deaf due to a defect in the inner
or middle ear will still be able to hear by bone
conduction.
Beethoven, could still hear his piano by placing
one end of his walking stick against it and
gripping the other end between his teeth.

How well can you hear?

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D. The Organ of Corti are neurons activated by
the hair cells vibrating

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V. The Other Senses

A. Touch Four skin senses - warm, cold,
pressure and pain
1. Pain
a. Phantom Limb sensations indicate that with
pain, the brain can misinterpret the spontaneous
central nervous system activity
b. Rubber-hand illusion
c. Gate Control theory
The theory that the spinal cord contains a
neurological gate that blocks pain signals or
allows them to pass on to the brain

The gate is opened by activity of pain signals
traveling up small nerve fibers and is closed by
activity in large fibers by information coming
from the brain
d. Pain control
Lamaze method of pain control operates by using
relaxation, counter-stimulation and distraction
Simple distraction alone also seems to work in
easing the pain of many medical procedures.

Virtual reality being used to distract a burn
patient
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2. Temperature
a. We have receptors for warm and cold
b. The sensation of hot is created by
simultaneous excitement of both warm and cold
receptors

C. Body senses
1. Kinesthesis(proprioception) the system for
sensing the body position and movement of
individual body parts
Ian Waterman

B. The Chemical Senses
1. Taste Five basic sensations
a. Sweet, sour, salty, umami, and bitter
b. Taste buds are replaced throughout our lives
c. We have less taste buds as we get older
d. Sensory interaction the principle that one
sense may influence another, as when the smell of
food influences the taste

2. Smell or olfaction
a. Like taste smell is a chemical sense
b. Receptor cells pick up different chemical
compositions
c. 1 of our genes are used to develop the many
different smell receptors in our nose

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Bell-ringer 1

Write 3 M/C questions on the material we have
already covered. Make one for each of the
following concepts
1. General Sensation
2. Vision
3. Audition

3. Pressure
a. We can feel very minor points of pressure
b. Pressure is sensed through specialized
receptor cells known as pancinian corpuscles

3. Vestibular sense the sense of body movement
and position including the sense of balance
4 Sensory Restriction
a. Includes loss of a sense such as sight,
resulting in increased perception in other senses
b. Also includes sensory monotony - like that of
a prisoner in solitary confinement
c. Has been used in therapeutic models
REST Restricted environmental stimulation
therapy
Has worked well with smokers who want to quit

Copy the phrase below and then provide the
punctuation that would make it a meaningful
sentence.
TIME FLIES I CANT THEYRE TOO FAST

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VI. Perception

A. Selective Attention
1. Selective Attention the focusing of
conscious awareness on a particular stimulus, as
in the cocktail party effect
2. The cocktail party effect the ability to
attend selectively to only one voice among many

Inattentional blindness a form of selective
attention in which we are focused in on one thing
that we miss obvious things in front of us
Changed Blindness a form of selective attention
in which we are focused in on one thing that we
do not notice changes in front of us

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Do you see circles with white lines or a cube.
Notice how the x moves from front to back
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Bell Ringer 2

Draw a picture that describes the scene below.
You are seated on the beach of a tropical island.
In front of you several palm trees sway in the
breeze. Young children can be seen playing in
the sand at the shore line while older children
and adults are splashing in the water. A
windsurfer glides by on the calm water while a
cruise ship sits off in the distance waiting to
enter port. Add one other object of your choice
that would be near to you and one that you can
see in the distance.

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3. The Ulric Neisser Basketball experiment
a. Subjects shown a video of two three man teams
passing a basketball
b. Asked to count the number of times black
shirted B-ball players passed the balls
c. Half way through the video a woman with a red
umbrella walked through the scene
d. Most subjects failed to notice the woman

B. Perceptual Illusions
1. The Muller-Lyer Illusion created in 1889 uses
two lines with arrows pointing in or out. The
carpentered world phenomenon comes into play here
as this illusion does not work well with people
who do not live in a square world.

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2. The Distorted Room illusion works by changing
the angles of the room, the images in the room
and the distance from the viewer.

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Optical Illusion Web Sites

Click to visit these sites

Color Cube.com
Just Riddles
NIEHS Kids Pages
Paintings
Brainbashers
Moillusions
Lightisreal.com
Optillusions.com
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More Illusions
Allpsych.com
Meltingpot
Premier photographer
Psycharts
MIT
Amazing Brain
Optical Illusions UK
Exploratorium
123opticalillusions
Bristol
Eye magic
Omnibrain
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Echalk
Optillusions.com
lycos
Optillusions.com
Info about Opt Illusions
Optillusions.com
Optillusions.com
Optillusions.com
Optillusions.com
Optillusions.com
Optillusions.com
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Try to count the black dots

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C. Perceptual Organization
1. Gestalt
a. an organized whole
b. Gestalt psychologists emphasize our tendency
to integrate pieces of information into
meaningful wholes
c. can be summarized by the statement the whole
is greater than the sum of its parts
d. The Law of Pragnanz states that we tend to
see things in their simplest form.

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2. Form perception
a. Figure Ground Relationships the
organization of the visual field into objects
(the figures) that stand out from their
surroundings (the ground

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b. Grouping the perceptual tendency to
organize stimuli into coherent groups
Similarity figures similar to each other we
group together
Proximity we group nearby figures together.
Closure we fill in gaps to create a complete,
whole object
Continuity We perceive smooth, continuous
patterns rather than discontinuous ones

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Grouping
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3. Depth Perception
a. Depth perception the ability to see objects
in three dimensions although the images that
strike the retina are two-dimensional allows us
to judge distance
b. Visual cliff a laboratory device for
testing depth perception in infants and young
animals

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c. The Gibson and Walk study involved placing 6
to 14month old babies on the edge of a safe
canyon (a visual cliff). Their mothers then
tried to convince the infant to cross the chasm.
Most of the babies refused to crawl across.
Newborn animals show similar results.

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d. Binocular cues depth cues such as retinal
disparity and convergence that depend on the use
of two eyes
retinal disparity a binocular cue for depth.
The fact that each eye sees a slightly different
picture. The brain combines the two and this
provides a clue as to how far away an object is

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Stereogram -
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convergence a binocular cue for depth the
extent to which the eyes converge inward when
looking at an object. The closer the object the
greater convergence
e. Monocular Cues distance cues such as linear
perspective and overlap, available to either eye
alone
interposition if one object blocks another we
perceive it as closer
Relative Size if we assume that two objects are
similar in size, we see the smaller one as being
farther away

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Aerial Haze hazy objects seem farther away
texture gradient a change from coarse, distinct
features to fine indistinct features. Up close
you see individual blades of grass, while you see
a field of green farther away
Relative height objects higher in our field of
vision seem to be farther away
Linear perspective parallel lines seem to
converge as distance increases

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4. Motion Perception
a. Without motion perception we would be unable
to do many of our everyday activities
b. Phi phenomenon when two or more adjacent
lights blink on and off in succession they will
appear as one moving light.
c. Stroboscopic movement when still pictures
are presented in rapid succession an illusion of
movement is created.
d. Autokinetic effect if a dot of light is
projected onto a screen in a dark room it will
appear to move

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5. . Perceptual Constancy
a. Perceptual constancy perceiving objects as
unchanging even as illumination and retinal
images change.
b. Size Constancy we perceive objects as being
the same size even though they are far away
a.k.a. Emmerts Law
c. Shape Constancy the fact that as the angle
an object is presented from changes our
interpretation of its shape stays constant

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Size and distance
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VII. Perceptual Interpretation

A. Perceptual Adaptation
1. the ability to adjust to an artificially
displaced or even inverted visual field.
2. For example students with upside down vision
goggles will eventually adapt.
B. Perceptual Set
1. A mental predisposition to perceive one thing
and not another.

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Schemas are concepts that help us mentally
organize our world.

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VIII. ESP

A. ESP The controversial claim that perception
can occur apart from sensory input. Said to
include telepathy clairvoyance and precognition
B. Parapsychology the study of paranormal
phenomena including ESP and psychokinetic powers.

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Bell-ringer 2