Download S & P Day 1a

Condensation Experiment
Sensory Adaptation
Sensation &
Perception
basic terminology
Scientific Names for the Six Senses (You
Should Know These)
•
•
•
•
•
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Seeing:
Hearing:
Tasting:
Smelling:
Sense of Touch:
Balance:
Visual
Auditory
Gustatory
Olfactory
Tactile
Vestibular
Sensation
Information coming into our brain from our sensory
receivers
Perception
The way the brain organizes and interprets the data
received by our senses
Can you have sensation without perception?
Prosopagnosia
Complete sensation in the absence of perception
Example of Prosopagnosia: FACE BLINDNESS
Bottom-up Processing
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
• Information processing guided by higher-level
mental processes as we construct
perceptions, drawing on our experience and
expectations.
• Top Down Processing explains how our
expectations and prior experiences guide our
perceptions.
THE CHT
Bottom Up Vs. Top Down
• What do you see?
Bottom Up vs. Top Down
What do You See?
Top-Down Processing
• Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it
deosn't mttaer in waht oredr the ltteers in a wrod
are, the olny iprmoetnt tihng is taht the frist and lsat
ltteer be at the rghit pclae. The rset can be a total
mses and you can sitll raed it wouthit a porbelm.
Tihs is bcuseae the huamn mnid deos not raed
ervey lteter by istlef, but the wrod as a wlohe.
Sensation vs. Perception
What do you see?
Sensation vs. Perception
What do you see?
Sensation vs. Perception
What do you see?
Making Sense of Complexity
“The Forest Has Eyes,” Bev Doolittle
How many faces do you see?
Psychophysics
• Psychophysics: study of the
relationship between physical
characteristics of stimuli and our
psychological experience of them
– Light - brightness
– Sound - volume
– Pressure - weight
– Taste - sweetness
Thresholds
Absolute Threshold
Minimum stimulation needed to detect a particular
stimulus 50% of the time.
Subliminal Messages
Messages presented below absolute thresholds –
not consciously perceived
“Subliminal Messages”
• Some have argued that humans still “pick up”
these messages that influence our
“unconscious.” Do these messages have
suggestive powers?
• Skeptics argue “Subliminal Messages” are
heavily influenced by top down processes.
• Example: Feeling “hungry” during subliminal
advertisements.
Mr. Subliminal
“Subliminal Messages”
• What does the research say?
Subliminal Message In Beer Ad?
Subliminal Messages In Money
Subliminal Message In
“The Lion King?”
Difference Threshold
Amount of change needed to notice that a change
has occurred.
Weber’s Law: The greater or stronger the
stimulus, the greater the change required to notice that a
change has occurred. The two stimuli must differ by a
constant minimum percentage (rather than a constant
amount), to be perceived as different.
JND = just noticeable difference
Sensation: Thresholds
• Signal Detection Theory: predicts how and
when we detect the presence of a faint stimulus
(signal) amid background stimulation (noise)
• Assumes that there is no single absolute
threshold
• What might a person’s detection of a
stimulus depend on?
Sensory Adaptation
Diminished sensitivity as a consequence of
constant stimulation.
Put a band aid on your arm and after awhile
you don’t sense it.
Now you see, now you don’t
The EYE
vision
key name
David HUBEL &
Torsten WIESEL
• Discovered that most cells in the visual
cortex only respond to particular
features. For example, maybe a cell responds only to lines
at this \ angle.
Wiesel was awarded the 1981 Nobel prize in Medicine and Physiology. His Nobel Lecture
was entitled 'The postnatal development of the visual cortex and influence of
environment.’ Wiesel recognized that covering one eye of a young animal could cause that
eye to lose its connection to the visual cortex.
Feature Detection
Ross Kinnaird/ Allsport/ Getty Images
Nerve cells in the visual cortex respond to
specific features, such as edges, angles, and
movement.
The Eye
Biology of Vision: Know the Steps
1. Light enters the eye through the cornea:
(transparent protector) and passes through
the pupil: (small opening/hole).
2. The size of the opening (pupil) is regulated by
the iris: the colored portion of your eye that is
a muscular tissue which widens or constricts
the pupil causing either more or less light to
get in.
Biology of Vision: Know the Steps
3. Behind the pupil, the lens, a transparent structure,
changes its curvature in a process called
accomodation, and focuses the light rays into an
image on the light-sensitive back surface called the
retina: where image is focused.
Biology of Vision: Know the Steps
4. Image coming through activates photoreceptors in
the retina called rods and cones (process
information for darkness and color).
5. As rods and cones set off chemical reactions they
form a synapse with bipolar cells which transducts
light energy into neural impulses.
6. The action potential travels along the ganglion cells
which send information up the optic nerve (bundle
of neurons that take information from retina to the
brain)
Biology of Vision: Know the Steps
7. The Optic Nerve carries neural information to be
processed by the Thalamus (sensory switchboard).
8. Thalamus sends information to the visual cortex
which resides in the occipital lobe.
9. The brain then constructs what you are seeing and
turns image right side up.
Parts of Retina
1. Fovea: central focal point of the retina, where cones
cluster.
2. Cones: photoreceptor located near center of retina
(fovea)
– fine detail and color vision
– daylight or well-lit conditions
3. Rods: photoreceptor located near peripheral retina
– detect black, white and gray
– twilight or low light
4. Bipolar Cells: create visual neural impulses
Most Common Errors In Vision
• Acuity: the sharpness of vision
• Nearsightedness:
– nearby objects seen more clearly
– lens focuses image of distant objects in front of
retina
• Farsightedness:
– faraway objects seen more clearly
– lens focuses near objects behind retina
COLOR
vision
Physical Characteristics of Light
Wavelength =
hue/color
Different wavelengths of light result in different colors.
Violet
Indigo
Blue
400 nm
Short wavelengths
Green
Yellow
Orange
Red
700 nm
Long wavelengths
Amplitude = intensity/brightness
COLOR mixing
Subtractive Color Mixing
mixing pigments (like paint). Result is:
Additive Color Mixing
mixing different colored lights. Result is:
Retina
Retina: The lightsensitive inner
surface of the eye,
containing receptor
rods and cones in
addition to layers of
other neurons
(bipolar, ganglion
cells) that process
visual information.
Photoreceptors
Let’s do a little experiment
to “map” our rods & cones
E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969
key name
Thomas YOUNG &
Hermann HELMOLTZ
• Trichromatic color theory (RGB) - some
cones are especially sensitive to red,
some to green, some to blue
Typical cases of Color Blindness
support the Trichromatic theory.
Opponent Process Theory
There are three opponent channels:
red vs. green
blue vs. yellow
& black vs.white
While the trichromatic theory defines the way the retina of the eye allows
the visual system to detect color with three types of cones, the opponent
process theory accounts for mechanisms that receive and process
information from cones.
Opponent Process Theory
Gaze at the middle of the flag.
When it disappears, stare at the dot and report
whether or not you see Britain's flag.
What just happened is called a NEGATIVE AFTERIMAGE