Transcript Exploring Our Senses

Sensation and Perception
 Directions: Turn to p. 198
 Sensation – sensory receptors and the
nervous system receive stimuli from our
world
 Bottom-up processing – begins with
the senses and goes to the brain (Ex.
Seeing light bounce off book into brain
Perception
 Perception – process of organizing and
interpreting information.

Top-down processing – information
processing guided by higher level mental
processes Ex. Saying brown, horse, man
or hat.
Thresholds
Absolute Thresholds – the minimum
stimulus necessary to detect a particular
stimulus 50% of time.
 Stimulus (light, odor, sound, pressure, taste)
 Ex. – standing on a mountain top, on a clear
night, we can see a candle flame 30 miles.
 Ex. We can taste a teaspoon of sugar in a
gallon of water.

EX. Sound on the television
Signal Detection Theory
 absolute thresholds vary depending on
experience, expectations, motivation and
level of fatigue
 This theory assumes there is no absolute
threshold
 Seeks to explain why the same person’s
reactions vary as circumstances change.

Ex. Mothers, soldiers, athletes.
Difference Threshold
 Activity Using 2 sheets of paper cover up
words on p. 202
 Difference Thresholds (aka just
noticeable difference- jnd)– the minimum
difference between two stimuli required
for detection fifty percent of the time.
 Q. Apply Difference Threshold to sugar
and water example?

Weber’s Law
 Weber’s Law – to be perceived as different,
two stimuli must differ by a constant
minimum percentage (rather than a constant
amount)
 Ex. Q. If you can tell a difference between
a 1 lb. weight and a 2 lb. weight…. Are
you then able to tell the difference
between a 49 lb. weight and a 50 lb.
weight?
 Q Why or Why not?
 Re: last para. on p. 201
Subliminal Thresholds
 below ones absolute threshold for
conscious awareness
 Q. What do you think of when you hear
the words subliminal message?
Can we be affected by
weak stimuli?
 Ex. Experimenters subliminally flashed a positive
scene (kittens or a romantic couple) or a negative
scene (werewolf or dead body) an instant before
showing a picture of a person. Participants
perceived the kitten or werewolf as a flash of
light. The participants gave a more positive rating
for the photos associated with the kitten or
romantic couple.
 Priming- the thought that is placed in the brain
immediately preceeding an ambiguous stimuli
will cause a person to to think one thing over
another …ape and pea…also yolk, toast
How do subliminal messages work?
 A word is flashed and immediately followed by
another stimulus that interrupts the brains
processing before conscious perception.
 We CAN process information/ sense information
without being aware of it.
Q. Can subliminal messages
influence buying habits or our
behaviors
Theatres- bottom of 195
 Ads- crystals of ice, Coors Brewing
 Blue on 200
 2nd para. 197
 Complete Critical Thinking Exercise Thresholds
 Subliminal Messages in Disney Movies – YouTube
 Issues - Knowmore.org (Disney’s image vs. reality)
 Walt Disney Brand (Phillip Morris, Altria), Haliburton
KBR), Harris Teeter and Kroger???
 critical thinking exercise
Sensory Adaptation
 – our diminishing sensitivity to an
unchanging stimulus.
 Q. Give examples?
 Moving your watch up your arm, ring on
finger, a terrible smell in the house,
Matthews train, swimming in cold water,
dark room – with time we become less
sensitive to these stimuli

Exploring Our
Senses
VISION AND HEARING
VISION
 Step 1 – GATHERING LIGHT
 Light is reflected off objects and gathered by
the eye
 Visible light to humans is only a small part of
the electromagnetic spectrum
The color we see depends
on 2 factors…
 Light Intensity - BRIGHTNESS
 Light Wavelength – COLORS
 (longest)ROYGBIV(shortest)
VISION
 Step 2 – LIGHT THROUGH THE EYE
 Light enters the eye through the cornea – protective
covering of the eye
 Light goes through the pupil – adjustable opening in
the center of the eye
 Iris is the muscle that controls the opening of the
pupil.
 Light is focused by the lens – transparent structure
behind the pupil
 Stare at your finger, then change focus to the wall, and
then to your finger… you should feel the muscles changing
the shape of your lens. Accomodation is the process
 As light passes through the lens, the image is
flipped upside down and inverted.
PARTS OF THE EYE
Images are inverted on
the retina
 The image of the "outside world" is inverted on our
retina, even though the world appears right side up.
Interestingly, if one wears prisms to make the retinal
image right side up, the world will appear inverted.
THE RETINA
 Rods – detect black, white, and
gray; necessary for peripheral
vision and twilight vision
 Some nocturnal animals have
retinas made up of nearly all
rods.
 Cones – concentrated near the
center of the retina (fovea),
function in daylight and well lit
conditions, detects detail and
color.
 Light strikes the rods and cones,
produces a chemical change to
neural signals, and activates
bipolar cells, which in turn
activate ganglion cells.
VISION
 Step 3 – Transduction
 Transduction – process by which our
sensory systems convert energy into
neural impulses. (prevalent with vision
and hearing)
WITHIN THE EYE
 Blind spot – where the optic nerve leaves the
eye
 Fovea – center of the retina with only cones
(no rods). Helps see details. (acuity)
 Focus on one word in the text, what happens to the other
words around that word?
BLIND SPOT
 Blind Spot – where the optic nerve leaves
the eye.
 Look on pages 203 in the text for a
demonstration of your blind spot.
Seeing in the Dark
 In dim light
 Cones become inadequate, rods remain
sensitive
 Pupils dilate in darkness to let more light to
reach the retina’s periphery
Nearsighted vs. Farsighted
 Nearsighted – light
rays from distant
objects focus in front
of the retina
 Seeing distant objects
is difficult
 Farsighted – light
rays from nearby
objects focus behind
the retina
 Seeing close objects is
difficult
Feature Detectors
 Feature detectors – nerve cells in the
brain (in the visual cortex) that respond to
specific features of the stimulus, such as
shape, angle, movement. Hubel and
Weisel. Colin Blakemore does terrible
things to kittens. For science!
 Recall the concept of brain specialization
and association areas from Ch. 2.
 Recall Fmri scanning 60 minutes- tools
Face Blindness
 Face Blindness: When everyone is a
stranger - CBS News
Parallel Processing
 Parallel processing –
The brain processes
several aspects of a
problem simultaneously
(contrasts with the stepby-step processing
found in a computer)
 The brain divides a
visual scene into color,
depth, motion and form.
Theories of Color Vision
 Young – Helmholtz
trichromatic theory –
We have three types of
cones in the retina.
(Cones that detect red,
blue and green) These
cones are activated in
different combinations to
produce all colors.
Theories of Color Vision
 Opponent-process
theory – Sensory
receptors in the
retina come in pairs.
If one sensor is
stimulated, then the
other is inhibited
from firing.
 Red/ green, Yellow/
blue, Black/ white
Opponent Processing
Theory
 The opponent processing theory explains
afterimages p. 213
Opponent Processing
Theory
 The opponent process
theory explains
colorblindness
 Colorblindness – if
dichromatic one cannot
see either red/green
shades or blue/yellow
shades, if
monochromatic one can
only see shades of gray.
 P.213
HEARING
 Audition – sense of hearing
 Sound waves are vibrations in the air (not
electromagnetic waves) and are collected
by our ears.
 Vibrations go through the process of
transduction. – Vibrations are changed
to neural impulses.
2 important characteristics
of sound waves
 Amplitude – height of the wave / determines loudness
 Loud sounds – tall waves
 Soft sounds – short waves
 Frequency – length of the wave / determines pitch
 High pitch – faster frequency
 Low pitch – slower frequency
Sound Travels Through
the Ear
 Sound enters the outer ear
 Waves travel down the ear canal (aka auditory canal)
until they reach the eardrum
 Eardrum – thin membrane that vibrates as the sound
waves hit it
 Eardrum connects to the middle ear
 Three bones in the middle ear – hammer, anvil, and
stirrup
 Passes vibrations of to the inner ear
 Inner ear
 Waves reach the cochlea – a snail shaped fluid filled tube
through which sound waves trigger neural impulses (this
is where transduction occurs) which travel to the brain.
PARTS OF THE EAR
SOUND LOCALIZATION
 Sound Localization
 Sound coming from the right, enters your
right ear sooner that your left
 The right ear also receives a more intense
sound than the left ear.
HEARING LOSS
 Hearing Loss
 Conduction hearing loss – due to damage
of the mechanical system that conducts
sound waves to the cochlea
 Ex. eardrum is punctured
 Sensorineural hearing loss (aka nerve
deafness) – due to damage to the cochlea’s
receptor cells or the auditory nerves.
 Ex. Loud noises, aging, heredity
Noise levels higher than
85 decibels are harmful…
Gate Control Theory
 The spinal cord contains a neurological
“gate.” Some pain messages have higher
priority than others. The high priority
message is sent and the “gate” swings open
and allows it to pass to the brain. The “gate”
closes for low priority messages – thus we
do not feel them. Endorphins can help the
gate to swing shut.
 Placing ice on the injured toe stimulates gate
closing