Transcript Unit 4- sensation

Sensation
Prosopagnosia anyone?
• http://www.youtube.com/watch?v=dxqsBk
7Wn-Y
• http://www.youtube.com/watch?v=q8cXus
7SNQY
Sensation
• The process by which our
sensory receptors and nervous
system receive stimulus from the
environment. (stuff inputed from
our 5 senses). A person with
prosopagnosia has normal
sensation
Perception
• The process of organizing and interpreting
sensory information, enabling us to
recognize meaningful objects and events.
The same person with prosopagnosia has
almost normal perception. She can
recognize some aspects of the person but
cannot put the whole picture together
•
Bottom Up v. Top Down Processing
• Bottom up – a progression from individual
elements to the whole (start small then
work your way up) (start focusing on trees,
then you pay attention to the forest).
• Top-down processing – start with the
forest and work your attention down to the
individual tree.
Bottom Up Look at the lines to
sort out the picture
Top down
• At first you see the big picture, then you
notice the parts (the faces)
Top-down processing
Top down processing
The word face makes you see the face first. It alters your perception.
Selective Attention
• The focusing of conscious awareness
on a particular stimulus.
Demonstration anyone?
Shhhh!!!!
• http://www.youtube.com/watch?v=vJG698
U2Mvo
An example of selective attention
is:
Cocktail Party Effect: ability to listen to
one voice among many.
Selective Attention
• 5 senses take in about 11,000,000 bits of
info a second. Consciously process about
40
• Possible problem with ADD peoplecannot block out stimuli
Inattentional Blindness or
Selective Inattention- failing to
see visible objects when our
attention is directed elsewhere
(gorilla)
• http://www.youtube.com/watch?v=QbgT6vDrmU
Change Blindness- failing to notice
changes in the environment
• http://www.youtube.com/watch?v=lEpekm
n0QOs
•
• https://www.youtube.com/watch?v=1nL5ul
sWMYc
• https://www.youtube.com/watch?v=ubNF9
QNEQLA
Choice Blindness
• http://www.youtube.com/watch?v=wRqywEwgTk
Thresholds
• Right now we are being hit with x-rays, radio waves,
infrared light, sound waves = Energy
• Most of which we are not aware – animals use another
sense- bats for example use echo location
• Our senses are only open a crack allowing us a
restricted awareness of this energy
• Psychophysics looks at the energy we can detect and its
effect on our psychological experiences
Absolute Threshold-The minimum amount of
stimulation necessary to detect a touch,
smell, sound, light,- The smallest amount
needed to detect a stimulus. Changes
• The minimum stimulation needed to
detect a stimulus 50% of the time.
Subliminal Messages
• Below your absolute threshold of conscious
awareness
• Subliminal messages prime people for a later
response
• Mostly a placebo- believe they work and they do
• http://www.youtube.com/watch?v=2Kur8p4yCao
&safety_mode=true&persist_safety_mode=1&sa
fe=active
Signal Detection Theory
• When we are able to
• Depends on a
detect the presence
person’s experience,
of slight stimuli
motivation and
among background
alertness
interference – noise
• People respond
differently to the same
stimuli
Difference Threshold
• The minimum difference that a person
can detect between two stimuli.
• Also known as Just Noticeable
Difference
Can you tell the difference?
Girls are better at this.
Weber’s Law
• The idea that, to perceive a difference
between two stimuli, they must differ by a
constant percentage; not a constant
amount. Must differ in weight by 2% ex- 50
oz wt must differ by 1 ounce, 100 oz by 2
oz
Application for Weber’s Law
• Would you drive 10 minutes away to save
$20 on a meal?
• Would you drive across town to save $100
on a $30,000 car?
• Since $100 is such a small percentage of a
car’s price, you don’t think of it as much money.
Sensory Adaptation
• Diminished sensitivity as a result
of constant stimulation.
Can you feel your underwear?
Transduction
Conversion of one form of
energy to another.
How is this important when studying
sensation?
Stimulus energies to neural impulses.
For example:
Light energy to vision.
Chemical energy to smell and taste.
Sound waves to sound.
Vision
We only use light energy to see.
Two physical characteristics of light help
determine our sersory experince of them?
Wavelength
• The distance from the peak of
one light wave to the peak of the
next.
•The distance determines the hue
(color) of the light we perceive.
Intensity
The amount of energy (brightness) in a
light wave.
Determined by the height or amplitude
of the wave.
Rods = b/w (light)
Cones = color
Parts of the Eye
• Light passes through the cornea which protects the eye
and pupil
• Pupil surrounded by the Iris- a colored muscle that
controls light
• Behind the pupil is the lens that focuses incoming light
rays onto the retina
• The lens focuses its rays by changing its curvatureaccommodation
• Fovea Area of sharpest vision – back of eye
• The retina houses the cones and rods (these are the
neurons that change light into neural impulses)
Parts of eye continued
• Cones = color and clear vision work best in bright light
rods- black and white, useful in dim light- neurons in the
retina that are light sensitive
• Optic nerve carries information to the brain via the
thalamus
• Brain that turns the image ride side up
• Where the optic nerve leaves the eye there are no
receptor cells creates a blind spot – no rods or cones (do
demo)
• Cones cluster near the fovea which is the retina’s area of
central focus
Receptors in the Human Ewye:
Rod Shaped Roda and
Feature detection
• Feature detection cells get their name
from their ability to respond to a scene’s
specific features: edges, lines angles,
movements ex: recognize faces in the
right temporal lobe just behind the right
ear. Damage to this ear may render you
incapable of recognizing faces
Figure 4.14 The telltale brain Looking at faces, houses, and chairs activates different brain areas in
this right-facing brain.
© 2011 by Worth Publishers
Parallel Processing
• The processing of several aspects of a
problem simultaneously.
Color
Motion
Form
Depth
How do we see in color?
What color is this dragon?
Color
• The dragon is anything but red.
• The dragon rejects the long
wavelengths of light that to us are
red- so red is reflected of and we see
it.
• Also, light has no real color.
• It is our mind that perceives the color.
Afterimages
• On the next few slides are afterimages.
• Stare at the center for about 20 seconds.
• Then I’ll explain why they happen.
• The phenomenon of a negative afterimage is
caused by opponent processes. After staring at
one object for a long time, the stimulated cells
use up resources, and begin to get 'tired'. Once
the object is removed, these cells will have to
fire below baseline for a bit to recover lost
resources. Meanwhile, their opponent cells will
fire at baseline- at a relatively higher rate. This
causes a negative afterimage. Try it out!
Stare at the red dot
Two major color theories
Young-Helmholtz Trichromatic
(three color) Theory
• Realized that any color can be created by
combining the light waves of three primary
color•So they guessed that we have 3 different
types of receptor cells in our eyes. Together
they can pick any combination of our 7 million
color variations.
•Most colorblind people simply lack cone receptor
cells for one or more of these primary colors.
An Explanation
• The red cones react most strongly to red light, but will
also react to colors close to red in the spectrum, so the
yellow light will stimulate them a little. Similarly, yellow
light will stimulate the green cones a little. So pure yellow
light will produce a tell-tale signal of some red and some
green. Our brain interprets this as yellow.
The brain can also be fooled by looking at a mixture of
red and green light. While red and green lights do not
actually mix physically, the mixture will stimulate the eye
in the same way as yellow light, so our brain interprets it
as yellow as well.
• If you can’t see the number then you are
missing one of your cones.
Are you Color Blind?
• http://www.youtube.com/watch?v=Mrz8Jsf
oy-c
• Basically, opponent processing color theory states that
nueronal activity is antagonistic in 3 different groups of
cells. In other words, stimulation of one cell causes its
partner to fire below baseline, and vice versa. There
are 3 oppositional pairs.
-red/green
-blue/yellow
-black/white
So for an example, if we stare at a red stop sign, all of
our 'red' cells will fire rapidly, while all of our green
cells will fire below baseline.
Stare at one figure for 30 seconds and then look at the white box and blink. Repeat
For the other figure.
Hearing
Aka: Audition
Hearing test
• http://www.youtube.com/watch?v=Vxcbpp
CX6Rk&feature=youtu.be
Frequency
the number of complete wavelengths that
pass through point at a given time. This
determines the pitch of a sound.
Amplitude is how loud the sound is. The higher
the crest of the wave is the louder the sound is. It
is measured in decibels.
Figure 4-5
The Human Ear
Slide 68
•http://www.youtube.co
m/watch?v=0jyxhozq89
g&list=PL2920A92123E
AF834&index=17
Transduction in the ear
• Sound waves hit the eardrum
then hammer then anvil then
stirrup then oval window.
• Everything is just vibrating.
• Then the cochlea vibrates.
• The cochlea is lined with mucus
called basilar membrane.
• In basilar membrane there are
hair cells.
• When hair cells vibrate they turn
vibrations into neural impulses
which are called organ of Corti.
• Sent then to thalamus up auditory
nerve.
It is all about the vibrations!!!
How do we perceive
differences in pitch?
There are two theories……..
Helmholtz’s Place Theory
• We hear different pitches
because different sound
waves trigger activity at
different places along the
cochlea’s basilar
membrane.
• High frequencies = large
vibrations near the
beginning of the cochlea’s
membrane
• Low frequency near the
end
Frequency Theory
• All the hairs vibrate
but at different
speeds.
Frequency Theory
• We sense pitch by the basilar membrane
vibrating at the same rate as the sound.
• But this theory has trouble explaining high
pitch sounds because our hairs cannot
vibrate at certain speeds.
• This problem can be explained using the
volley principle.
Why do we have two ears?
Allows us to hear
stereophonic or 3
dimensional hearing
Hearing loss
• Conduction Hearing Loss: caused by damage to mechanical
system of ear. Punctured eardrum, or tiny bones in the middle
ear lose the ability to vibrate
– Sensorineural hearing loss (nerve deafness): caused by
damage to cochlea’s receptor cells or to auditory nerves.
More common, Causes: loud noise, biological changes:
aging, heredity. Solution: Cochlear implant- highly
controversial
Touch
• Use skin the largest
organ in the human
body
• Hairy skin detect
movement and
pressure
• Glaborous skin- no
hair cells more
sensitive: lips, palms,
bottoms of feet
• Pressure has
identifiable receptors
• 4 basic skin
sensations: pressure,
warmth, cold and pain
Kinesthetic Sense
• Tells us where our
body parts are.
• Sense of the
position and
movement of your
body
• Proprioception- loss
of all feeling below
the neck cannot
move (video)
Without the kinesthetic sense
you could not touch the button
to make copies of your buttocks.
Touch
•http://www.youtube.co
m/watch?v=FKxyJfE831
Q&list=PL2920A92123
EAF834&index=97
Vestibular Sense
• Tells us where our
body is oriented in
space.
• Our sense of
balance.
• Located in our
semicircular canals
in our ears.
What is vestibular sense?
• Vestibular sense: monitors your head and your body’s
movements. This equilibrium is in your inner ear
• Fluid in the inner ear which is found in the vestibular
sacs and semicircular canals moves when you rotate
your head
• This movement activates hair cells that send messages
to your cerebellum which allows you to sense your body
position and maintain balance.
• Spinning round and stopping quickly fools your brain that
you are still spinning and you get dizzy. It is an illusion
• Once your fluid and kinesthetic receptors return to
neutral you no longer feel dizzy
• Let’s try it
Pain- your body’s way of telling
you something is wrong
• Biological Influences-No
central location for pain
receptors. Many ways to
trigger pain.
• Noceptors-sensory receptors
that detect harmful temps,
pressure and chemicals
• Gate-control theory- idea that
your spinal cord has a
neurological gate that blocks
pain signals or allows them to
pass to the brain
• Endorphins help
Pain Control
• Placebos- when given fake pain killing placebos
the brain was tricked into releasing real ones
“Believing becomes reality
• Distracting with pleasant images
• Exercise
• Massage
• Pain is in the brain, diverting the brain’s attention
may bring relief
Smell and Taste
Was I born to love peanut
butter & jelly?
What is the bigger question here?
Nature versus Nurture
Figure 4-6
The Olfactory System
Slide 89
Why do we study smell and taste
together?
• SENSORY INTERACTION: the principle
that one sense may influence another.
Sensory Interaction
• SI happens with other senses
• McGurk effect- hear someone say ba but the
mouth looks like is says ga we perceive da
• Some people experience synesthesia- one
sensation produces another examples: hearing
something may activate color sensitive regions
and produce color
• Seeing a number can provoke a taste
Annoying MrGurk effect Video
• http://www.youtube.com/watch?v=jtsfidRq
2tw
Sensation and Perception
Synesthesia

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Unusual condition in which stimulus of one
type, such as sound also gives rise to
another experience such as color
Colored Hearing… most common
Synesthesia is different for different people
May argue vigorously with each other about
color of Tuesday or taste of Beatles music
Testing Synesthesia

As quickly as possible, find the 2’s
Testing Synesthesia
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So….Was I born to love
peanut butter & jelly?
Lets take a look at the
Nature perspective first.
How do we taste?
•Taste (and smell) are
chemical senses.
What is the central muscle
involved in taste?
Taste
• We have bumps on our
tongue called papillae.
• Taste buds are located
on the papillae (they are
actually all over the
mouth).
• Sweet, salty, sour and
bitter and savory.
• Taste buds reproduce
every 2 weeks
• In older people taste
decreases
PTC Strips
But what about smell?
Can our sense of smell
be biologically based?
Gender related odors
• Can you smell the difference between?
Hands,
Breath,
Shirts
So can we smell the difference?
• Well….yes and no.
Pheromones
•Chemical messengers that are picked up
through our sense of smell.
•Founded in the early 1930’s by studying
silkworms.
•Jury is still out on whether they exist in
humans. Best evidence we have comes out
of the university of Chicago.
•Figure 4.30 The olfactory brain Information from the taste buds (yellow arrow) travels to an area
of the temporal lobe not far from where the brain receives olfactory information, which interacts with
taste. The brain’s circuitry for smell (red arrow) also connects with areas involved in memory storage,
which helps explain why a smell can trigger a memory explosion.
•© 2011 by Worth Publishers
Lets not forget about Nurture