Transcript Sensation PP - Ms. Hilsinger`s Blog

Chapter 6
Part I: Introductory Ideas & Terms
Quiz Questions-9 Nov
1. The purpose of the pupil is to
a.
b.
c.
d.
e.
Focus light on the retina
Process color.
Allow light into the eye.
Enable night vision
Detect specific shapes
2. Cells that respond to specific edges, lines, angles and
movements are called
a.
b.
c.
d.
e.
Rods.
Cones.
Ganglion cells.
Feature detectors
Bipolar cells.
Nov 9
1. The purpose of the pupil is to
a.
b.
c.
d.
e.
Focus light on the retina
Process color.
Allow light into the eye.
Enable night vision
Detect specific shapes
2. Cells that respond to specific edges, lines, angles and
movements are called
a.
b.
c.
d.
e.
Rods.
Cones.
Ganglion cells.
Feature detectors.
Bipolar cells.
Sensation & Perception
To represent the world, we must detect physical
energy (a stimulus) from the environment and
convert it into neural signals. This is a process
called sensation.
When we select, organize, and interpret our
sensations, the process is called perception.
“Perception creates an interpretation of
sensation.”
Illusions…
Bottom-up Processing (Sensation)
Analysis of the stimulus begins with the sense
receptors and works up to the level of the brain
and mind.
Letter “A” is really a black blotch broken down into
features by the brain that we perceive as an “A.”
Top-Down Processing (Perception)
Circle Test
Information processing guided by higher-level
mental processes as we construct perceptions,
drawing on our experience and expectations.
THE CHT
Aocincdrg to rsecaerh at Cmdiagbre
Uinservtiy, it desno’t mtetar in waht
oredr the lteters in a wrod are, the olny
ipranmoett tinhg is taht the fsrit and
lsat lteetr be at the rghit pclae. The rset
can be a ttaol mses and you can siltl
raed it whotuit a pbeolrm. Tihs is
bcuseae the haumn mnid deos not raed
ervey lteter by istlef, but the wrod as a
wlohe.
Psychophysics
Established by Gustav Fechner in 1860 it is the study of
the relationship between physical characteristics of stimuli
and our psychological experience with them.
Physical World
Psychological
World
Light
Brightness
Sound
Volume
Pressure
Weight
Sugar
Sweet
Absolute Threshold
The minimum stimulation needed to detect a
particular stimulus 50% of the time.
Absolute Threshold
Absolute
Threshold
Intensity
No
No
Yes
Yes
Yes
Observer’s Response
Detected
Tell when you (the observer) detect the light.
Signal Detection Theory
Signal Detection Theory predicts how and
when we detect the presence of a faint
stimulus/signal in the midst of
background stimulation/”noise”
According to this theory, there is no single
absolute threshold and experiences,
expectation, motivation and tiredness play
a role in stimulus detection.
Difference Threshold
Difference Threshold (also called just noticeable
difference or JND) is the minimum difference between
two stimuli required for detection 50% of the time,
Difference
Threshold
No
No
Yes
Observer’s Response
Tell when you (observer) detect a difference in the light.
Subliminal Threshold
http://yeli.us/Flash/Fire.html
Subliminal Threshold
occurs when stimuli are
below one’s absolute
threshold for conscious
awareness.
“Hungry? Eat Popcorn”
(1/3000 of a second for 18% increase!)
James Vicary’s 1957 Picnic study in
New Jersey was a hoax
Weber’s Lawquarter test
Ernst Weber noted that two stimuli must differ by a
constant minimum percentage (rather than a
constant amount), to be perceived as different.
Stimulus
Constant (k)
Light
8%
Weight
2%
Tone
3%
$1.00 → $1.01
$1.00 → $1.10
Sensory Adaptation
salt water test
fruit marker test
Diminished sensitivity is a consequence of constant stimulation.
 If you just enter a room, you will smell its natural odor,
but after a while you won’t notice the smell
 Your body “gets used” to the temperature of the water
 After a while you do not notice the band-aid on your arm
• What good does sensory adaptation do for us?
- It allows us to “filter out” stuff that doesn’t change
and immediately recognize changes in our
environment.
Part II: Transduction
(Sight, Hearing, Touch, Taste & Smell)
Transduction = In sensation, the transformation of
stimulus energy into neural impulses.
Phototransduction is the conversion of light
energy into neural impulses that the brain
can understand.
The Stimulus Input: Light Energy
Visible
Spectrum
Wavelength (Hue)
Hue (color) is the
dimension of
color determined
by the
wavelength of
the light.
Wavelength is
the distance from
the peak of one
wave to the peak
of the next.
Wavelength (Hue)
Violet
Indigo
400 nm
Short wavelengths
& High frequency
Blue
Green
Yellow
Orange
Red
700 nm
Long wavelengths &
Low frequency
Different wavelengths of light result
in different colors.
Intensity (Brightness)
Intensity is the
amount of
energy in a wave
determined by
the amplitude
(height).
It is related to
perceived
brightness.
Intensity (Brightness)
Blue color with varying levels of intensity.
As intensity increases or decreases, blue color
looks more “washed out” or “darkened.”
The Eye
1.
2.
3.
4.
Cornea: Transparent
tissue where light enters
the eye.
Iris: Muscle that
expands and contracts to
change the size of the
opening (pupil) for
light.
Lens: Focuses the light
rays on the retina.
Retina: Contains
sensory receptors that
process visual
information and sends
it to the brain.
Retinal arteries/veins
Fovea
Aqueous
humor
Ciliary muscle
The Lens
Lens is the transparent
structure behind the
pupil that changes shape
to focus images on the
retina.
Accommodation is the
process by which the eye’s
lens changes shape to help
focus near or far objects
on the retina.
Problems with Visual Acuity
Nearsightedness:
A condition in
which nearby
objects are seen
more clearly than
distant objects.
Farsightedness:
A condition in
which faraway
objects are seen
more clearly than
near objects.
The Retina: orange paper test. eye movement test
Retina: The lightsensitive inner surface
of the eye, containing
receptor rods
(black/white) and
cones (color) in
addition to layers of
other neurons
(bipolar, ganglion
cells) that process
visual information.
Bipolar cells receive
messages from
photoreceptors and
transmit them to
ganglion cells, which
form the optic nerve.
Photoreceptors
Optic Nerve, Blind Spot & Fovea
Optic nerve: Carries neural impulses from the eye to the brain.
Blind Spot: Point where the optic nerve leaves the eye because there
are no receptor cells located there. This creates a blind spot.
Fovea: Central point in the retina around which the eye’s cones
cluster.
Visual Information Processing
Feature detectors: nerve cells in the brain that respond to
specific features of the stimulus, such as shape, angle or
movement
“You look with your eye, but see with the brain”
Optic nerves connect to the thalamus
in the middle of the brain, and the
thalamus connects to the visual
cortex.
David Hubel & Torsten Wiesel
won the Nobel Prize in
Medicine in 1981
Parallel Processing
Processing of several aspects of the stimulus
simultaneously is called parallel processing. The
brain divides a visual scene into subdivisions such
as color, depth, form and movement etc.
Theories of Color Vision
Young-Helmholtz Trichromatic (three-color theory):
Based on behavioral experiments, Helmholtz
suggested that the retina should contain three
receptors that are sensitive to red, blue and green colors.
Problem With
the Trichromatic Theory?
• How can colorblind
people who cannot see
red and green, still see
yellow (which
according to the
Trichromatic Theory is
a mix of red and green
light)?
Color Blindness- test
Genetic disorder (more males) in which people are
blind to green or red colors. This supports the
Trichromatic theory.
Ishihara Test
Opponent Process Theory
• Hering proposed that we process
four primary colors combined in pairs
of red-green, blue-yellow, and blackwhite.
• The retina and thalamus have
neurons that are turned “on” by one
of the colors of the pair but turned
“off” by the opposite color
• Dual-Process Theory combines the
Trichromatic Theory with the
Opponent Process Theory
Afterimages can be created by the
Opponent Process Theory
Additive Color Mixing
If three primary colors (lights) are mixed, the
wavelengths are added and the color white is the result.
Subtractive color
mixing= mixing
three primary colors
(pigments) subtracts
wavelengths (fewer
wavelengths are
reflected back) and
the color black is the
result.
Color Constancy
optical illusion video
Color of an object remains the same under different
illuminations. However, when context changes the
color of an object may look different.
Acoustical Transduction
“You have to have an ear to produce a sound”
Conversion of sound waves into neural impulses in
the hair cells of the inner ear.
Sound waves are composed of compression
of air molecules.
Frequency (Pitch)
sounds kids can hear, adults cannot
Frequency
(pitch): The
dimension of
frequency
determined by
the wavelength
of sound.
Wavelength: The
distance from
the peak of one
wave to the peak
of the next.
Intensity (Loudness)
Intensity
(Loudness):
Amount of energy
in a wave,
determined by the
amplitude, relates
to the perceived
loudness.
Loudness of Sound
120dB
70dB
Quality (Timbre)
Quality (Timbre): Characteristics of sound from
a zither and a guitar allows the ear to distinguish
between the two.
Zither
Guitar
The Ear- video on hearing
Outer Ear: The Pinna
collects sounds.
Middle Ear: Chamber
between eardrum and
cochlea containing three
tiny bones (ossicles:
hammer, anvil, stirrup)
that concentrate the
vibrations of the eardrum
on the cochlea’s oval
window.
Inner Ear: Innermost part
of the ear, containing the
cochlea, semicircular
canals, and vestibular sacs.
Pinna
aka Ossicles
(Hammer, Anvil &
Stirrup)
Cochlea
Cochlea: Coiled, bony, fluid-filled tube in the
inner ear that transforms sound vibrations to
auditory signals.
Theories of Audition
 Place Theory suggests that sound frequencies stimulate the
basilar membrane at specific places resulting in perceived pitch.
 Also theorized by Helmholtz
 Explains how we hear high pitched sounds well but
doesn’t explain how we hear low pitched ones very
well
Theories of Audition
Frequency Theory states that the rate of nerve
impulses traveling up the auditory nerve
matches the frequency of a tone, thus
enabling us to sense its pitch.
Sound
Frequency
100 Hz
200
Auditory Nerve
Action Potentials
Theories of Audition
• The problem with the Frequency Theory is
that neurons cannot fire faster than 1000
times per second
• So again, there must be a combination of
theories (i.e. Place and Frequency Theory
principles work together somehow)
Localization of Sounds
hand clapping activity; boy who
sees video
Because we have two ears, sounds that reach
one ear faster than the other ear cause us to
localize the sound.
1. Intensity differences
2. Time differences
Time differences as small
as 1/100,000 of a second
can cause us to localize
sound. The head acts as a
“shadow” or partial sound
barrier.
Hearing Loss
Conduction Hearing Loss: Hearing loss caused by
damage to the mechanical system that conducts sound
waves to the cochlea.
 Examples: damage to eardrum or
hammer/anvil/stirrup (vibration is affected)
Sensorineural Hearing Loss: Hearing loss caused
by damage to the cochlea’s receptor cells or to the
auditory nerve, also called nerve deafness.
- most people born deaf suffer this type of loss
Cochlear implants are electronic devices
that enable the brain to hear sounds.
Hearing Deficits
Older people tend to hear low frequencies well but
suffer hearing loss when listening for high
frequencies.
Body Position & Movement
The sense of our body parts’ position and movement is
called kinesthesis. The vestibular sense monitors the head
(and body’s) position and helps with maintaining balance.
Vestibular sense is governed by fluid filled sacs in
semicircular canals of the inner ear.
Whirling Dervishes
Wire Walk
Touch (a.k.a. Tactile Senses)
The sense of touch is a mix of four distinct skin
senses—pressure, warmth, cold, and pain.
Skin SensesOnly pressure has identifiable receptors. All other
skin sensations are variations of pressure, warmth,
cold and pain.
Pressure
Burning hot
Vibration
Vibration
Cold, warmth and pain
Pain
Pain tells the body that something has gone
wrong. Usually pain results from damage to the
skin and other tissues. A rare disease exists in
which the afflicted person feels no pain.
Ashley Blocker suffers from Congenital Analgia.
She feels neither pain nor extreme hot or cold.
Biopsychosocial Influences
Gate-Control Theory
Proposed that our spinal cord contains neurological
“gates” that either block pain or allow it to be sensed.
Pain can be controlled by a number of
therapies including, drugs, surgery,
acupuncture, exercise, hypnosis, and
even thought distraction.
Smell (a.k.a. Olfactory Sense)
Smell is a chemical sense. Odorants enter the nasal
cavity to stimulate 5 million receptors to sense smell.
Unlike taste, there are many different forms of smell.
Age, Gender, and Smell
Ability to identify usually smell peaks during early
adulthood, but steadily declines after that. Women
are better at detecting odors than men.
Smell & Memories
The brain region for
smell (in red) is closely
connected with the
brain regions involved
with memory (limbic
system).
That is why strong
memories are made
through the sense of smell.
Taste (a.k.a. Gustatory Sense)
Traditionally, taste sensations consisted of sweet,
salty, sour, and bitter tastes. Recently, receptors for
a fifth taste have been discovered called “Umami”.
Sweet
Sour
Salty
Bitter
Umami
(savory/meaty)
http://www.pbs.org/wgbh/nova/sciencenow/0404/01.html
Sensory Interaction
When one sense affects another sense, sensory
interaction takes place.
So, the taste of strawberry interacts with its smell
and its texture on the tongue to produce flavor.