Sensation and Perception
Sensation: detecting stimuli from the body or surroundings.
Perception: interpreting and organizing sensations into
meaningful patterns.
Bottom-Up Processing
• Info processing
that analyzes raw
stimuli entering
through our
sensory systems.
• We use the
features on the
object itself to
build a perception.
• Takes longer than
top-down but is
more accurate.
Top-Down Processing
• Info processing that
draws from
expectations and
experiences.
• I _ant ch_co_ate ic_
cr_am.
• If you see many old
men in glasses, you are
more apt to process a
picture of an old man
(even when you may be
in error).
What if we could sense everything?
Life would hurt.
So we can only take in a window of what is out there.
Psychophysics: studies the relationship between
physical stimuli and our psychological experiences to
them.
Absolute Threshold
• The minimum amount of stimulation one
can detect through a given sense 50% of
the time.
Absolute Thresholds
• Taste: 1 teaspoon of sugar dissolved in two
gallons of water.
• Smell: 1 drop of perfume diffused throughout a
three-room apartment.
• Touch: the wing of a bee falling on your cheek
from a height of 1 centimeter (.39 inch).
• Vision: a candle flame seen from 30 miles on a
clear, dark night.
• Hearing: the tick of a watch from 20 feet in
very quiet conditions.
•
http://www.phys.unsw.edu.au/jw/hearing.html
Difference Threshold
(Just Noticeable Difference)
The minimum amount of change in stimulation that can be detected.
Signal Detection Theory
• States that absolute
thresholds are not really
absolute.
• Things like motivation or
our physical state can
effect what we sense.
A mom could sleep through a war, but if
one of her kids even whimpers, she is up!!!
Subliminal Stimulation
• Below one’s absolute threshold for
conscious awareness.
Do subliminal messages work?
Most evidence suggests it’s not effective.
Subliminal Messages: The Early Years
• James Vicary claimed to have
flashed the words “eat popcorn”
and “Drink Coca-Cola” on a movie
screen for 1/200th of a second,
every 5 seconds during the movie
Picnic.
• He claimed popcorn sales
increased 58% and Coke sales
increased 18%.
• Vicary’s experiment was never
successfully replicated
• He later acknowledged the study
was a fraud.
The Middle Years: Embedded images and text
• Embedded images
and text are
subliminal messages.
• This ad for
Tanqueray allegedly
contains a phallic
symbol.
Recent Years: Product placement
• Product placement is a
form of supraliminal
persuasion.
• Subtle, perhaps, but
not subliminal.
Embedded images in Disney movies
• The Little Mermaid
– The artist who
painted this scene
claimed the
resemblance to a
phallic symbol was
unintentional.
More Disney embedding
• The Rescuers Down Under
(who’s in the window?).
• The Lion King.
More embedding…
• Pall Mall cigarettes
and embedding?
– Some claim that
the banner on the
bottom of the
Kent cigarette
package shows two
KKK Klansmen.
• Pepsi and embedding
– The graphics on
the cans line up to
form the word
“SEX.”
Embedding as a conspiracy theory
• Examples of embedded
images appear to be
isolated cases.
– The incidents appear
to be pranks rather
than organized
marketing
strategies.
– The mere existence
of subliminals does
not prove their
effectiveness.
Are there hidden messages in song lyrics?
• Can the mind detect
lyrics that might be
played in reverse?
• http://jeffmilner.com/b
ackmasking/index.html
Sensory Adaptation
• Tendency of sensory
receptors to respond less and
less to constant stimulation
(Diminished sensitivity).
Do you feel your underwear all day?
Selective Attention
• An example of selective
attention is the cocktail party
effect which is the ability to
focus one's attention on a
single talker among a mixture
of conversations.
• Cocktail-party activities.
Selective Attention & the Stroop Effect
Your right brain tries to say the color, your left reads the word.
Energy vs. Chemical Senses
Energy Senses
Chemical Senses
Vision
• Our most dominating sense.
• The eye is like a camera (it
needs light).
Phase One: Gathering Light
•
•
•
•
•
The height of a wave gives us it’s intensity (brightness).
The length of the wave gives us it’s hue (color).
ROY G BIV
The longer the wave the more red.
The shorter the wavelength the more violet.
Phase One: In the Eye
The Blind Spot is where there are no Rods or Cones.(Blind Spot Activity)
Structures of the Eye
• Iris – regulates the amount of light going into the eye
(colored part).
• Pupil – black opening where light enters.
• Lens – focuses light on the retina.
• Retina – has layers of sensory cells:
Cones – (6 million) for color and daylight vision.
Most highly concentrated near the fovea (back center
of the eye).
Rods – (120 million) for peripheral and night vision.
Located along the sides of the retina.
(do the peripheral vision activity) *** And note the
rods and cones numbers in your text are backwards!!!
The Retina
Phase Two: Vision In the Brain
We have specific cells that
see the lines, motion, curves
and other features of this
turkey. These cells are
called feature detectors.
Show The Brain (Module 8)
“Elementary Visual Concepts” (3-6 min.)
• Goes to the Visual
Cortex located in the
Occipital Lobe of the
Cerebral Cortex.
• It’s here that we
interpret what we are
looking at.
Visual Pathway
Show Secrets of The Mind - “Blindsight” (15-23 min.)
Facts on Color Vision
Colors we experience depend on the relative
degree of stimulation to the cones.
Pigments mixed together absorb
more wavelengths than a single
pigment (subtractive color mixing)
Wavelengths added together
stimulate more cones (additive
color mixing)
Color Vision
Two Major Theories
Trichromatic Theory
Three types of cones:
• Red
• Blue
• Green
• These three types of
cones can make millions of
combinations of colors.
• Does not explain
afterimages or color
blindness well.
Opponent-Process theory
The sensory receptors
come in pairs.
• Red/Green
• Yellow/Blue
• Black/White
• If one color is
stimulated, the
other is inhibited.
Afterimages
Afterimages
• When the eyes are then diverted to a blank
space, the adapted photoreceptors send out
a weak signal and those colors remain muted.
However, the surrounding cones that were
not being excited by that color are still
"fresh", and send out a strong signal. The
signal is exactly the same as if looking at the
opposite color, which is how the brain
interprets it.
Color Blindness
Missing
Red
Missing
Green
Missing
Blue
Types of color blindness:
• Red / Green (most common)
• Blue / Yellow
• Total colorblindness
• Most colorblind people
are dichromats – they
lack one kind of
photopigment.
• Males more likely to be
colorblind.
Hearing (Audition)
Our auditory sense
Hearing is produced by sound waves.
Frequency: the number of complete wavelengths
that pass through point at a given time. This
determines the pitch of a sound or how high or low
a sound is.
Amplitude or Intensity: is how loud the sound is.
The higher the crest of the wave is the louder the
sound is. It is measured in decibels.
Write
 this
Structures In the Ear
• Sound waves hit the eardrum;
then the middle ear bones.
• Everything is just vibrating.
• Then the cochlea vibrates.
• The hair cells (cilia) in the
fluid filled cochlea vibrate.
• Then signals are sent to
auditory nerve, up to the
thalamus and on to the
auditory cortex.
It is all about the vibrations!!!
The Ear
Sound Localization Demonstration
Hearing Deficits
Older people tend to hear low frequencies well but
suffer hearing loss when listening for high frequencies.
Deafness
Conduction Deafness
• Something goes wrong
with the sound and the
vibration on the way to
the cochlea.
• You can replace the
bones or get a hearing
aid to help.
Nerve (sensorineural) Deafness
• The hair cells in the cochlea
get damaged.
• Loud noises (concerts) can
cause this type of deafness.
• NO WAY to replace the hairs.
• Cochlea implant is possible.
Localization of Sounds
Because we have two ears, sounds that reach
one ear sooner than the other ear cause us to
localize the sound. It’s also louder for one ear.
Taste and Smell
Why do we study smell and taste together?
• SENSORY INTERACTION: the principle
that one sense may influence another.
Taste
• We have bumps on our tongue
called papillae.
• Taste buds are located on the
papillae.
• Sweet, salty, sour, bitter and
umami (savory).
• Bitterness detectors – critical
because most poisons are bitter.
• Sour detectors – detect bad
foods.
• Built-in salt and sugar needs for
survival.
Back of the tongue
Tip of the tongue
Sci. American: Tasters and Supertasters; PTC Strips Activity and Food Coloring.
Smell (Olfaction)
• Olfactory Cells – receptor
cells that collect molecules
of odor.
• Olfactory bulbs – receives
an electrical signal and
generates a “code” that is
sent to the brain for
interpretation.
Touch (Cutaneous Senses)
• Cutaneous receptors
are located in our skin.
• Three types: pressure,
cold, heat, & pain.
• Gate Control Theory
Gate Control Theory
• Contends that there is an area in the
spinal cord that can act like a “gate” and
either inhibit pain messages or transmit
them to the brain.
• When tissue is injured, the small nerve
fibers activate and open the neural gate,
and you feel pain.
• Large-fiber activity closes the pain gate,
turning pain off.
Phantom Limb Pain
• Phantom limb pain is a
frequent complication
of amputation.
• Client complains of
pain at the site of the
removed body part,
most often shortly
after surgery.
•
Show Phantom Limb Video (Secrets of the
Mind)
Vestibular Sense
• Tells us where our body
is oriented in space.
• Our sense of balance.
• Located in our
Semicircular Canals in
our ears.
Kinesthetic Sense
• Tells us where our body
parts are.
• Receptors located in our
muscles, joints and tendons.
Without the kinesthetic sense
you could not touch the button
to make copies of your buttocks.
Perception
Gestalt Psychology
• Gestalt means “an organized whole.”
• These psychologists emphasize our tendency to
integrate pieces of information into meaningful
wholes.
Gestalt Psychology
• To perceive forms, we must
organize the visual field
into objects (figures) that
stand out from their
surroundings (ground).
• This is figure-ground
perception.
Gestalt Grouping Principles
• Gestalt psychologists focused on how we GROUP objects
together.
• We innately look at things in groups and not as isolated
elements.
• Proximity (objects that are close together are seen as
being part of same group).
• Similarity (objects similar in appearance are perceived as
being part of same group).
• Continuity (objects that form a continuous form are
perceived as part of the same group).
• Closure (we fill gaps in if we can recognize it).
Gestalt Grouping Principles
Depth Perception
• The ability to see objects in three dimensions
although the images that strike the retina are
two dimensional.
• Allows us to judge distance.
Depth Cues
• Eleanor Gibson and her
Visual Cliff Experiment.
• If you are old enough to
crawl, you are old enough to
see depth perception.
• We see depth by using two
types of cues:
• Monocular Cues (w/ 1 eye)
• Binocular Cues (w/ 2 eyes)
Monocular Cues
• Interposition: if something is blocking
our view, we perceive it as closer.
•Relative Size: if we know that two objects
are similar in size, the one that looks smaller
is farther away.
•Relative Clarity: we assume hazy
objects are farther away.
More Monocular Cues
• Texture Gradient: distant objects look
smoother than closer objects.
•Relative Height: things higher in our
field of vision, they look farther away.
•Relative Motion: things that are closer
appear to move more quickly.
•Linear Perspective: parallel lines seem to
converge with distance.
Monocular Cues
•
•
•
•
•
•
Examples of…
Linear Perspective
Interposition
Relative size
Texture gradient
Relative Motion
Motion Perception
• Stroboscopic effect (flip book effect).
• Phi phenomenon (blinking neon lights;
like the marquee in
front of the school).
Binocular Cues
• We need both of our
eyes to use these cues.
• Retinal Disparity –
slightly different
images produces by the
retina of each eye.
• Convergence - degree
to which our eyes turn
inward to focus on an
object.
Perceptual Constancy
• Perceiving objects as unchanging even as
illumination and retinal images changes.
Perceptual Constancy
•
•
•
•
Types of Constancy
Shape Constancy
Size Constancy
Lightness Constancy
Perceptual Set
• Mental predisposition to perceive
one thing and not another.
•
http://www.ted.com/talks/michael_shermer_on_believing_strange_things.html
• What you see in the center picture
is influenced by a perceptual set.
(A good example of top-down
processing).
• Based on schemas (mental
frameworks).
Illusions = inaccurate perceptions
• Not always a “mistake” by us; sometimes
we change what we perceive so that the
world makes more sense.
• Sometimes we make guesses in the
context of what we think should be the
case.
Famous Illusions
Muller-Lyer Illusion
Ames Room
Extrasensory Perception
• Extrasensory perception (ESP): the
ability to perceive events without
using normal sensory receptors.
• Parapsychology: the field that studies
ESP and other paranormal phenomena.
Types of ESP
– Telepathy: the ability to read minds.
– Clairvoyance: the ability to perceive
objects or events.
– Precognition: the ability to predict the
future.
– Psychokinesis: the ability to move objects.
There Is Little Scientific Evidence
for Extrasensory Perception!!!
• Reasons for skepticism:
– Many published ESP studies have used
flawed research methodologies or failed to
detect outright fraud by those they were
testing.