Download Psych B – Module 9

Module 09
Sensation
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.
– 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?
Signal Detection Theory:
What is it, and why is it a significant accomplishment for modern psych?
• What’s that on the x-ray: scar tissue or a tumor???
• Grew out of the Cold War.
– To improve our ability to detect incoming nuclear warheads in
time to respond appropriately.
• National security depends on accurate signal detection!
• Set of formulas and principles that predict when we will
detect the presence of a faint stimulus (signal) amid
background stimulation (noise)
– Detection depends on qualities of the stimulus, the
environment, and the person who is detecting.
Signal Detection Theory (cont.)
• 3 Kinds of variables:
– 1. Stimulus
• How bright is the blip on the radar screen?
– 2. Environmental
• How much distracting noise is there in the room with the
radar equipment?
– 3. Organismic
• Is the operator properly trained and motivated?
• Now used in ways other than militaristic:
– Air traffic control, make sure one plane isn’t too close
to another, accurately detecting tumors, etc.
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;
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
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.
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
• Lens not letting you
focus?
– Get contacts/glasses
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
• 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?
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.
Parts of the Ear – Semicircular Canals