Download 10 Sensation

Sensation and
Perception
Sensation
• The process by which our
sensory systems (eyes,
ears, and other sensory
organs) and nervous
system receive stimuli from
the environment
Sensation
• 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 is be light waves,
sound waves, smell, taste,
or touch.
Perception
• The process of organizing and
interpreting sensory
information
• How we recognize,
interpret, and organize our
sensations
Bottom-Up Processing
• Information processing that
focuses on the raw material
entering through the eyes,
ears, and other organs of
sensation
• This is the sensation part of
awareness
Top-Down Processing
• Information processing that
focuses on expectations and
experiences in interpreting
incoming sensory information
• This is the perception part of
your awareness
Top Down Processing can lead to
errors!
do you see the tiger? (top down)
do you see the hidden tiger? (bottom up)
do you see the mountains? (top down)
do you see the face? (bottom up)
Module 9: Sensation
Thresholds
Absolute Threshold
• A threshold is an edge or a
boundary
• For sensations, it is the point
where you either sense a
stimulus or don’t
Technically, its “The minimum
stimulus that a person can
detect 50% of the time”
Absolute Detection Threshold
• The minimum intensity of
energy required to produce
sensation in a receptor cell
• 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
• One testable way to
determine the thresholds for
various people is through
SIGNAL DETECTION
• Incremental changes in
sound, taste, etc. are made to
test for reactions in people.
Tone tests (hearing) are an
example.
Signal Detection Results
• Hit
– signal present and
sensed
• Miss
– signal present but not
sensed
• False Alarm
– signal absent, but
sensed
• Correct Rejection
– signal absent, and not
sensed
• IE. Frog eye’s have receptor cells
that fire only in response to small,
dark, moving objects. Theoretically,
a frog would starve to death while
knee-deep in motionless flies.
Remember…………
…ABSOLUTE means
we either see it,
smell it, taste it….or
we don’t!
Difference Threshold
• The minimum difference that a person
can detect between two stimuli 50% of
the time
• Also called just noticeable difference
• (JND)
Hey!
someone
Is it just
must
me or
have
did
suddenly
turned on
get
another
a little
brighter
light!
in here?!
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
need to add 10 lbs. to 100 pounds to
make it noticeable.
Sensory Adaptation
• When exposed to a stimuli over
a period of time there will be a
diminished sensitivity to it
• If a stimulus is constant and
unchanging, eventually a person
may fail to respond to it
Example of Sensory Adaptation
• A hot tub – after a certain period
of time no longer seems as hot
Let’s see how good your
senses are!
TAKE THE AWARENESS TEST
ON THE NEXT SLIDE!
Selective Attention
• Focusing conscious awareness on a
particular stimulus (sense) to the
exclusion of others
Selective Attention Example
• Walking
down the
hallway – all
5 senses are
firing. What
grabs your
attention?
Selective hearing
• Do you think it exists?
Selective Attention
• Focusing conscious awareness on a
particular stimulus to the exclusion
of others
• The ability to focus on one stimulus
at a time
• Allows a person to function in a
world filled with many stimuli
Module 9: Sensation
The Visual System:
The Nature of Light
Module 9: Sensation
The Visual System:
The Structure of the
Visual System
Cornea
• The clear bulge on the front of the
eyeball
• Begins to focus the light by bending it
toward a central focal point
• Protects the eye
Parts of the Eye – Cornea
Iris
• A ring of muscle tissue that forms the
colored portion of the eye; creates a hole in
the center of the iris (pupil)
• Regulates the size of the pupil by changing
its size--allowing more or less light to enter
the eye
Parts of the Eye - Iris
Pupil
• The adjustable opening in the center of
the eye that controls the amount of light
entering the eye (surrounded by the iris)
• In bright conditions the iris expands,
making the pupil smaller.
• In dark conditions the iris contracts,
making the pupil larger.
Parts of the Eye - Pupil
Lens
• A transparent structure behind the pupil;
focuses the image on the back of the eye
(retina)
• Muscles that change the thickness of the lens
change how the light is bent thereby focusing
the image
• Glasses or contacts
correct problems in the
lens’ ability to focus.
Parts of the Eye - Lens
Nearsighted - Myopia
Farsighted - Hyperopia
Retina
• Light-sensitive surface with cells that
convert light energy to nerve impulses
• At the back of the eyeball
Parts of the Eye - Retina
Receptor Cells
• These cells are present in every sensory
system to change (transduce) some
other form of energy into neural
impulses.
• In sight they change light into neural
impulses the brain can understand.
• Visual system has two types of receptor
cells – rods and cones
• Visual
receptor
cells located
in the retina
• Can only
detect black
and white
• Respond to
less light
than do
cones
Rods
• Visual receptor
cells located in
the retina
• Can detect
sharp images
and color
• Need more
light than the
rods
• Many cones
are clustered in
the fovea.
Cones
Fovea
• The central focal point of the retina
• The spot where vision is best (most
detailed)
Parts of the Eye - Fovea
Visual Processing in the Retina
Visual Processing in the Retina
Visual Processing in the Retina
Visual Processing in the Retina
Optic Nerve
• The nerve that carries visual information
from the eye to the occipital lobes of the
brain
Parts of the Eye – Optic Nerve
• The point at which the optic nerve
travels through the retina to exit the
eye Blind Spot
• There are no rods and cones at this
point, so there is a small blind spot in
vision.
Parts of the Eye – Blind Spot
Module 9: Sensation
The Visual System:
Color Vision
Color Vision
• There are two theories of
color vision:
–Trichromatic Theory
–Opponent-Process
Theory
Can you see what is in the middle?
Trichromatic Theory
Young-Helmholtz Theory
• 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.
Color Deficient Vision
• People who lack one of the three
types of cones
• Usually the red or green receptors
are missing
• Usually referred to as color
blindness
• In inherited and found more in
males
Red-Green Color Blindness
Opponent-Process Theory
• Sensory receptors in the retina
come in pairs:
–Red/Green
–Yellow/Blue
–Black/White
•Only one side is “on” at a
time
Opponent
Process
Theory
ON”
“OFF”
red
green
green
red
blue
yellow
yellow blue
black
white
white black
Afterimage Effect
Opponent-Process Theory
• If one sensor is stimulated, the
other is inhibited
• If one sensor is overstimulated, and fatigues, the
paired sensor will be activated,
causing an afterimage
Module 9: Sensation
Hearing:
The Nature of Sound
Sound
• Sound, like light, comes in waves
• Sound is vibration
• Features of sound include:
–Pitch
–Hertz
–decibels
Pitch
• A sound’s highness or
lowness in tone
• Dependent on the frequency
of the sound wave – the more
“waves per second” the
higher the frequency or pitch
• Is measured as hertz (Hz)
Hertz (Hz)
• A measure of the number of
sound wave peaks per second;
measures “frequency”
• Determines the pitch of the sound
• Human hearing goes from 20 Hz
to 20,000 Hz
Decibel (dB)
• A measure
of the height
of the sound
wave
• Determines
the loudness
of the sound
• Sometimes
called
amplitude
Module 9: Sensation
Hearing:
The Structure of the
Auditory System
PINNA
Also called the
auricle. The
visible part of
the outer ear.
• It collects sound and directs it
into the outer ear canal.
Parts of the Ear – Auditory Canal
Auditory Canal
• The opening
through
which sound
waves travel
as they
move into
the ear for
processing
• Ends at the
eardrum
THE MIDDLE EAR
Eardrum
• Also called the tympanic
membrane. A thin membrane
that vibrates when sound
waves reach it.
• it transfers sound vibration
from the air to the tiny bones
of the middle ear
• Can be damaged by objects in
the ear or exceptionally loud
noises
Parts of the Ear – Tympanic
Membrane
Ossicles
• Three tiny bones that transfer
sound waves from the
eardrum to the cochlea
• Hammer, anvil and stirrup
– Fun fact: the stirrup is the
smallest bone in the human
body – only .25 cm
Parts of the Ear - Ossicles
Oval Window
• The point on the surface of
the cochlea which receives
the sound vibration from the
ossicles
• As the oval window vibrates,
the fluid in the cochlea
vibrates.
Parts of the Ear – Oval Window
• The
Ossicles
amplify
the
vibration
of the
eardrum
Cochlea
• A hearing organ where sound
waves are changed into
neural impulses
(transduction)
• The major organ of hearing
• Filled with fluid; a snail
shaped body tube
Parts of the Ear - Cochlea
Hair Cells
• The receptor cells for hearing in the
cochlea that change sound vibrations
into neural impulses
• Transduction!
Movement of the fluid causes
the hair cells to move which
causes TRANSDUCTION!
Parts of the Ear - Hair Cells
Auditory Nerve
• The nerve that carries sound
information from the ears to the
temporal lobes of the brain
Parts of the Ear – Auditory Nerve
Semicircular Canals
• Organs in the inner ear used
in sensing body orientation
and balance (vestibular
sense)
• Relies on fluid in the canals
• Spinning in circles disrupts
the fluid.
Parts of the Ear – Semicircular Canals
Divisions of the Ear
• Ear’s structure can be divided into:
–The outer ear
–The middle ear
–The inner ear
Divisions of the Ear
Divisions of the Ear
Divisions of the Ear
Parts of the Ear
• Sound waves to Outer
Ear• Ear Canal, Eardrum
(waves bounce on
membrane)
• Middle Ear- hammer,
anvil, stirrup
• Small bones vibrated
by waves
• Oval Window
(membrane vibrates)
• Inner Ear- sound
waves ripples fluid in
cochlea and activates
hair cells
Problems with hearing
• Conduction deafness
(middle ear damage)
• Nerve deafness (hair cell
or auditory nerve damage)
How do we hear?
Place Theorydifferent
frequencies in
sound waves
cause
vibrations at
different places in the cochlea
Low
Frequencies
High
Frequencies
Frequency Theory- different
frequency of the sound wave
vibrates the inner ear at a
different rate
EUSTACHIAN
TUBE
• A tube that connects the middle ear to the back
of the nose; it equalizes the pressure between
the middle ear and the air outside. When you
"pop" your ears as you change altitude (going
up a mountain or in an airplane), you are
equalizing the air pressure in your middle ear.
Module 9: Sensation
Hearing:
Sound Localization
Localization of Sound
• Locating where sound is originating
from
• Done through two cues:
–Which ear hears the sound first?
–Which ear hears the louder sound?
Localization of Sound
Problems with hearing
• Conduction deafness
(middle ear damage)
• Nerve deafness (hair cell
or auditory nerve damage)
• Cochlear
Implant
Module 9: Sensation
Other Senses:
Taste
(Gustation)
Taste
• Taste is a chemical sense.
• The little bumps on our tongues
are actually called papillae
• Inside some of these papillae are
clumps of taste cells.
• These clumps of cells are actually
the taste buds.
• On average, adults
have about 7,500
taste buds.
• These receptor cells
are located in the
tongue and in the
mouth.
• When food
dissolves on these
receptors,
TRANSDUCTION
occurs
• Damaged taste
receptor cells are
replaced within a
few days to 2 weeks
Taste
• Taste Sensations
–sweet
–sour
–salty
–bitter
- umami (savory-msg)
Supertasters
• People with an abundance of taste
receptors
• Approximately 25% of the population
Nontasters
• People with a minimum of taste
receptors
• Taste with less intensity than the
rest of the population
• Approximately 25% of the
population
Module 9: Sensation
Other Senses:
Smell
• Smell is a chemical sense.
• Olfactory receptors/cells in the
upper nasal passages detect
molecules in the air.
• Taste and smell interact to
produce flavor.
Olfactory Cells
• The chemical
receptor cells for
smell
• Located in the
nasal passages
Smell
Smell
Smell
Other Senses:
Touch
Touch
• Touch receptors are on the skin
• Four basic skin senses are
– Pain
– warmth
– cold
– pressure
• All skin sensations are a combination
of these four basic senses
Sensitivity of Diff body to pain
Most Sensitive
• Back of knees
• Neck region
• Bend of elbow
Least Sensitive
• Tip of the Nose
• Sole of foot
• Ball of thumb
• Pain messages
travel on one set of
nerve fibers
containing pain
gates.
• The gates are open
when pain is felt.
• Other sensory
messages go
through another set
of fibers.
• The non-pain fibers
can close the pain
gates to stop the
sense of pain.
Gate-control Theory of Pain
• Pain messages travel on one set of nerve
fibers containing pain gates.
• The gates are open when pain is felt.
• Other sensory messages go through
another set of fibers.
• The non-pain fibers can close the pain
gates to stop the sense of pain.
Module 9: Sensation
Other Senses:
Body Senses
Kinesthetic Sense
• The system for sensing
the position and
movement of individual
body parts
• Relies on receptor cells
from the muscles and
joints
• One’s leg “falling asleep”
is a disruption of the
kinesthetic sense
Vestibular Sense
• The system for sensing body
orientation and balance
• Relies on fluid in the semicircular
canals of the inner ear
• Spinning in circles disrupts the fluid.
Parts of the Ear – Semicircular Canals
The End