Transcript Psych B – Module 9

Module 09
Sensation
https://www.youtube.com/
watch?v=unWnZvXJH2o
Let’s see if you labeled correctly:
Let’s take in our surroundings:
• What do you see?
– What shapes are around you? What colors?
• What sounds are you listening to?
• What can you feel?
– Is your clothing comfortable, what about your chair?
• What do you taste?
• Are there any odors?
• This awareness of the world around you is
called sensation.
Sensation
• The process by which our sensory systems
(eyes, ears, and other sensory organs) and
nervous system receive stimuli from the
environment
• Bottom-up processing:
– Information processing that focuses on the
raw material entering through the eyes, ears,
and other organs of sensation
Perception
• The process of organizing and
interpreting sensory information
• Top-Down Processing:
– Information processing that focuses on
expectations and experiences in interpreting
incoming sensory information
Sensation and Perception
• Do you see some marks that look the same as
others, but are meant to be interpreted
differently?
– Sensation brings image from paper to your brain, a bottom-up
process of gathering environmental info through the senses.
– Perception involves knowing what to make of the individual
marks in the sentence. This top-down interpretation relies on
your experiences with, and expectations about, language.
Thresholds:
an edge or a boundary
What are absolute thresholds
and difference thresholds,
and how do they differ?
Absolute & Difference Threshold
• Absolute threshold:
– The minimum stimulation needed
to detect a particular stimulus.
– Ex: Dimmest star in the sky would
be right at the absolute threshold
for vision.
• What about for taste/hearing?
• Difference threshold
– Aka: just noticeable difference
– Minimum difference that a person
can detect b/t 2 stimuli.
– The smallest detectable change in a
stimulus.
• When does sound become too loud or
when is something too tight?
Sensory Adaptation
How does sensory adaptation make your life easier?
• When we filter out the non-changing aspects of our
environment.
– If a stimulus is constant and unchanging, eventually a
person may fail to respond to it.
– Diminished sensitivity as a result of constant stimulation.
– EX: getting into a swimming pool that seems rather chilly
• What happens at first? After a while?
– EX: ever look for your sunglasses and realize they are on
your head?
Selective Attention
How does selective attention relate to effective study skills?
• Focusing conscious awareness on a particular
stimulus to the exclusion of others
– You can’t pay attention to every single little
thing at once!
• The ability to focus on one stimulus at a time
– Ever blocked out sound to help you study/sleep?
• Allows a person to function in a world filled
with many stimuli
So… what do you see?
• You can attend
to one view or
the other:
– Old or young
woman
• You can earn
learn to switch
back and forth.
• You cannot see
both images at
once.
Module 9: Sensation
The Visual System:
The Nature of Light
What is light?
Electromagnetic Energy
• Light enters the eye as waves of
electromagnetic energy.
• An energy spectrum that includes Xrays, radar, and radio waves .
– A small portion of the spectrum includes
light visible to the human eye
The Electromagnetic Spectrum
• Light is a form of
electromagnetic
energy. This energy
travels in waves,
ranging from short
gamma rays to long
radio waves. The
human eye can
detect only a small
portion of these
waves, the visible
spectrum, as light.
1st characteristic of waves: Hue
• The color of light as determined by the
wavelength of the light energy
– What color is this power point slide?
• Includes: red, orange, yellow, green,
blue, indigo and violet (ROY G BIV)
• The eye can detect 7 million separate
hues
Wavelength
2nd characteristic of waves: Amplitude
• The brightness of
light as determined
by height of the
wave
• The taller the wave,
the brighter the color
– Thus greater
amplitude stronger
hue.
Module 9: Sensation
The Visual System:
The Structure of the
Visual System
What are the major parts of the visual
system, and what roles do these parts
play in our ability to see?
• Light first strikes the
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
Cornea
• Colored part
• A ring of muscle tissue
that forms the colored
portion of the eye
• Regulates the size of the
pupil by changing its
size--allowing more or
less light to enter 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.
• Ex: wake up in middle of night go to the
bathroom, turn on light and watch your
pupil shrink in the mirror.
– Restricting light b/c it’s too bright for you.
• 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
• Lens not letting you
focus?
– Get contacts/glasses
Lens
Nearsightedness & Farsightedness
• With normal vision, the lens
changes in thickness to
cause the light rays from a
viewed object to converge at
the retina.
– The result is a clear focused
image.
• In a nearsighted person’s
eye, the lens causes light
rays from distant objects to
converge in front of the
retina, which blurs the
image.
• If a person is farsighted, the
lends causes light rays from
close objects to converge
behind the retina.
• Corrective lenses, help the
eye’s own lens focus the
image correctly.
Retina
• All other structures
• Made up of three
(cornea, pupil, iris,
layers of cells
lens) direct traffic –
– Receptor cells
move visual info to
retina!
– Bipolar cells
• Important processing
– Ganglion cells
center at the back of
the eyeball
• Light-sensitive surface
with cells that convert
light energy to nerve
impulses
Retina layer: Receptor Cells
• Deepest layer of retina.
• Can change light energy into nerve impulses
that the brain can interpret.
– Without this, the brain would be completely
isolated from information in the outside world.
• Two different types:
– Rods and cones
• Visual receptor cells located in the retina.
• Different in appearance and function.
Comparing and Contrasting:
Rods
Cones
• Can only detect black
and white.
• Have a lower absolute
threshold.
• Respond to less light
than do cones.
• Under dim light, only
rods respond and you
see the worlds in shades
of gray.
• Less of them.
• Can detect sharp images
and color.
• Need more light.
• Many cones are
clustered in the fovea,
where your vision is
best.
• The
central
focal
point
of the
retina
• The spot
where
vision is
best
(most
detailed)
Fovea
Two remaining layers of the retina:
• Bipolar Cells:
– Middle layer of retina.
– Gather information from the rods and cones and
pass it on to the ganglion cells
• Ganglion Cells:
– Top layer of retina.
– Receive info from bipolar cells and transmit it
through their axons, which together form the optic
nerve.
Visual Processing in the Retina
The
nerve
that
carries
visual
info.
from
the eye
to the
occipital
lobes of
the
brain.
Optic Nerve
Parts of the Eye – Blind Spot
(check page 166 in your book)
• The point at
which the
optic nerve
travels
through the
retina to exit
the eye.
• The lack of
receptor rods
and cones at
this point
creates a
small blind
spot.
Module 9: Sensation
The Visual System:
Color Vision
What are the two theories of color vision?
Which one offers the best explanation of how
we see colors?
#1:Trichromatic (three-color) Theory
• Theory of color vision that says cones
are “tuned” to be sensitive to red, green
and blue light
– All the colors we see are a combination of
these three colors.
• Based on work of Helmholtz and Young
• Similar to the design of a color TV
• Subtractive Color Mixing
– When mixing colored paints,
each new color SUBTRACTS
(soaks up) another
wavelength.
– Red, blue, and yellow
combine to make black paint.
• Additive Color Mixing
– When mixing colored lights,
each new color ADDS
another wavelength.
– Red, green, and blue combine
to make white light.
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
• Sometimes people don’t even know the
problem exists.
#2: Opponent-Process Theory of Color
• Ewald Hering’s theory that says color is
processed in opponent pairs of color:
– Red-green, yellow-blue, black-white
• Light that stimulated one half of the pair
inhibits the other half
• Explains the afterimage effect
Afterimage Effect:
Stare at the white dot in the middle w/o blinking
So…what do you see?
Really great video to watch (45 min)
http://www.dailymotion.com/video/xq1
p3e_national-geographic-test-yourbrain-episode-1-payattention_shortfilms
Hearing:
The Nature of Sound
What is 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
• Dependent on the
frequency of the
sound wave
• Is measured as hertz
(Hz)
Hertz (Hz)
Decibel (dB)
• Determines pitch
• Determines loudness
• A measure of the
• A measure of the
number of sound
height of the sound
wave peaks per
wave
second; measures
– Sometimes called
amplitude
“frequency”
• Human hearing goes • Named after
Alexander Graham
from 20 Hz to 20,000
Bell.
Hz
Module 9: Sensation
Hearing:
The Structure of the
Auditory System
What are the major components
of the auditory system?
What is the function of each?
• The opening
through
which sound
waves travel
as they
move into
the ear for
processing
• Ends at the
tympanic
membrane
(eardrum)
Parts of the Ear – Sound Waves
Auditory Canal
Tympanic Membrane (eardrum)
• The tissue barrier that transfers sound
vibration from the air to the tine bones
of the middle ear
• Can be damaged by objects in the ear or
exceptionally loud noises
Parts of the Ear – Tympanic Membrane
• Three tiny
bones that
transfer
sound
waves from
the eardrum
to the
cochlea
• Hammer,
anvil and
stirrup
Ossicles
• A hearing
organ where
sound waves
are changed
into neural
impulses
• The major
organ of
hearing
• Filled with
fluid
• snail shaped
body tube
Cochlea
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
Hair Cells
• The receptor cells for hearing in the cochlea that
change sound vibrations into neural impulses
• Similar to the rods and cones within the eye
• The nerve
that carries
sound info.
from the
ears to
the
temporal
lobes of
the brain
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
Hearing: Localization of Sound
How do you identify where a sound is coming from?
• Locating where
sound is originating
from
• Done through two
cues:
– Which ear hears
the sound first?
– Which ear hears
the louder sound?
Other Senses: #1: Taste
• Taste is a chemical sense.
• Receptor cells are located primarily on
the tongue and in the mouth.
• Four different tastes:
– Salty, sweet, sour and bitter
• Damaged taste receptor cells are
replaced within a few days.
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
#2: Smell
• Smell is a chemical sense.
• Olfactory 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
#3: Touch
• Touch receptors are on the skin
• Four basic skin senses are
– Pain, warmth, cold, and pressure
• All skin sensations are a combination of
these four basic senses
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 nonpain fibers can close the pain
gates to stop the sense of pain.
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.