Download Sensation and Perception

Sensation and Perception
Sensation - your “window” to the world; taking in
information
Perception - interpreting what comes in your
“window”; interpreting/understanding
information taken in
VIDEO - Intro to Sensation / Perception
Psychophysics:
Basic Concepts
and Issues
Essentials
of Sight
The Visual
System:
Perceptual
Processes
The Auditory
System:
Hearing
The Other
Senses:
Taste, Smell,
and Touch
Bottom-up vs. Top-down Processing
Bottom-up
Top-down
• Begins with sense
receptors and works UP
to the brain
• Associated with
Sensation
• Can be thought of as
“first” of the two
• Information processing
guided by “higher level”
mental processes
• Associated with
Perception
• Can be thought of as
“second” of the two
Difference Threshold
(Just Notable/Noticeable Difference)
The smallest amount of change needed to detect a change in a stimulus
Absolute Threshold
Do you hear anything?
• The minimum stimulation needed to detect a
stimulus 50% of the time.
Weber’s Law
• Computes the "Just
Noticeable
Difference".
• The change needed is
proportional to the
original intensity of
the stimulus.
• The more intense the
stimulus the more
change is needed to
notice the difference.
Ernst Weber (1795 – 1878)
• Anatomist /
physiologist
• introduced the “Just
Noticeable
Difference” (JND)
concept
– expressed the
principle of
difference threshold
Gustav Fechner (1801 – 1887)
• key figure in
“Psychophysics”
– science of
quantitative
relationships between
sensation and their
stimuli
• expressed the JND
as a mathematical
formula and called it
“Weber’s Law”
Subliminal Messages
• Stimuli below our
absolute threshold.
• Do Subliminal
Messages work?
– Evidence suggests
minimal influence
– Probably a placebo
effect
Subliminal Messages
• Stimuli below our absolute threshold.
• Do Subliminal Messages work?
– Evidence suggests minimal influence
– Probably a placebo effect
– examples
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Signal Detection Theory
• predicts how and when
we detect the presence
of a stimulus
• assumes that “absolute
threshold” is dependent
on context/situation
• says that detection
depends on experience,
expectations,
motivation, fatigue
Sensory Adaptation
• The diminished sensitivity as a
consequence of constant stimulation
Sensory Transduction
• transforming stimulus
energy into neural
impulses
– In vision, light waves are
transformed into neural
impulses and messages
from the eye to the
thalamus and then to other
parts of the brain.
– In hearing, sound waves
are transformed into
neural impulses and
messages from the ear to
the auditory cortex of the
temporal lobe.
Remember the characters from Sky
High? They could change from
their physical, bodily form into
something else altogether.
Click the image above to watch the
characters transform.
Vision
VIDEO - How Does Vision Work?
• Our most
“dominating” sense
• Visual capture
Phase One: Getting the light in
the eye
Phase Two: Transduction
Cones (explain rods)
Phase Three: 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.
• Goes to the Visual
Cortex located in
the Occipital Lobe
of the Cerebral
Cortex
• Feature Detectors
• Parallel Processing
David Hubel (1926-2013) /
Torsten Wiesel (1924 - ????)
• researched visual sensation / perception
• Nobel Prize (Physiology/Medicine) for their
work discovering feature detectors
Parallel Processing
• The processing of several aspects of an
object simultaneously.
Color
Motion
Form
Depth
Color Vision
Two Major Theories
Why is her top green?
Trichromatic Theory
(Young-Helmholtz 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.
Afterimages
Color-Deficient Vision
 People who
suffer red-green
blindness have
trouble
perceiving the
number within
the design
Opponent-Process theory
The sensory receptors
come in pairs.
• Red/Green
• Yellow/Blue
• Black/White
• If one color is
stimulated, the
other is inhibited.
Opponent Process- Afterimage Effect
5
Perceptual Ideas
Top-Down Processing
If you see many old men in
glasses, you are more apt to
process a picture of an old
man rather than that of a
mouse.
• We perceive by filling the
gaps (using past
experiences and schema)
• I _ant ch_co_ate ic_
cr_am.
• Perceptual Set – a mental
predisposition; the
experiences, assumptions,
and expectations that
influence our perception
Selective Attention
• The focusing of
conscious awareness
on a particular
stimulus.
5th Period
– Selective Attention
causes change (or
inattentional)
blindness.
– cocktail party effect
selective attention to
one voice among many
Second Period
Gestalt Psychology
• Gestalt – an organized whole; from German
for “form” or “whole”
• Gestalt psychologists emphasized the
tendency to integrate pieces of information
into a meaningful whole.
• Gestalt Psychology says that we innately
look at things in groups, not as isolated
elements.
• “The whole is greater than the sum of it’s
parts.”
Similarity
Proximity
Psychophysics:
Basic Concepts
and Issues
Essentials
of Sight
Closure
Continuity
The Visual
System:
Perceptual
Processes
The Auditory
System:
Hearing
The Other
Senses:
Taste, Smell,
and Touch
Grouping & Gestalt Psychology
• Proximity - group objects
that are close together 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 same
group
• Connectedness – objects
that are uniform and
linked are perceived as
single units
• Closure - we fill gaps to
create a whole or
complete image
Closure
Figure Ground Relationship
Visually, our first
perceptual decision
is “What is the
figure?” in the
image and “What is
the ground?”
(background).
The figure ground relationship can also
be applied as a principle of auditory
perception.
Depth Perception
experiment
• Eleanor Gibson - Visual
Cliff Experiment
• If you are old enough to
crawl, you are old
enough to see depth
perception.
• We see depth/distance
by using two cues that
researchers have put in
two categories:
– Monocular Cues
– Binocular Cues
Binocular Cues
• We need both of our
eyes to use these cues.
• Retinal Disparity - as
an object comes closer
to us, the differences
in the images for our
eyes becomes greater.
 “finger sausage”
 3-D movies
• Convergence - as an
object comes closer,
our eyes have to come
together to keep
focused on the object
Monocular Cues
• You really only need
one eye to use these.
– Linear Perspective
– Interposition
– Relative Size
– Texture Gradient
– Light / Shadowing
Perceptual Constancy
• Objects change in our
eyes constantly as we or
they move….but we are
able to maintain content
perception
 Shape Constancy
 Size Constancy
 Color Constancy
 Brightness Constancy
o However, color and
brightness also depend on
context!
Perceptual Adaptation
inverted vision
program 7: start @ 15:39
• The ability to adjust to an artificially
altered visual field
Hearing
Our auditory sense
The Ear
Transduction in the ear
• Sound waves hit the eardrum
then anvil then hammer 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.
• Sent then to thalamus up
auditory nerve.
It is all about the vibrations!!!
Hearing – Perceiving Pitch
Place Theory
• Different pitches
stimulate different
parts of the basilar
membrane within the
cochlea
• Best explains high pitch
sensation
Frequency Theory
• The rate of nerve
impulses matches the
frequency of tone
• Sound waves of 100
waves per second = 100
pulses per second travel
up the auditory nerve
• Best explains low pitch
sensation
Deafness
Conduction Deafness
Nerve (Sensorineural) Deafness
• Something goes wrong
with the
mechanical/vibration
process in hearing.
• Hearing aids to help.
• The hair cells in the cochlea
get damaged.
• Loud noises can cause this
type of deafness.
• NO WAY to replace the hairs.
• Cochlear implant is possible.
Touch
• Sensory receptors are located in
our skin
• “Gate-Control Theory” of Pain
– spinal cord blocks or allows pains
signals to pass to brain
– Phantom limb
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,
bitter, and umami .
• Sensory Interaction –
principle that one
sense influences
others (i.e. – taste &
smell)
Olfactory System
Why are smells often involved with emotions?
Kinesthetic Sense
• tells us where our
body parts are
• uses receptors
located in our
muscles, joints, and
tendons
You would use kinesthesis to
touch the button to make copies
of your buttocks.
Vestibular Sense
• tells us where our
body is oriented in
space.
• our sense of balance.
• located in our
semicircular canals
and vestibular sacs
of the inner ear.
Motion Perception
• Stroboscopic Effect
 a rapid series of slightly
varying images perceived
as moving images (flip
book, “old” movies)
• Phi Phenomenon
illusion of movement created when two or more ----lights next to each other blink on and off
Parapsychology
• the study of
paranormal phenomena,
including ESP and
psychokinesis
• ESP – extrasensory
perception; perception
outside of sensory
perception
–
–
–
–
Telepathy
Telekinesis
Clairvoyance
Precognition
Human Factors Psychology
• branch of Psychology
• explores…
– how human and
“machines” interact
– how “machines” and
physical environments
can be adapted to
human behaviors
FINISHED FILES ARE THE
RESULT OF YEARS OF
SCIENTIFIC STUDY
COMBINED WITH THE
EXPERIENCE OF MANY
YEARS.
FINISHED FILES ARE THE
RESULT OF YEARS OF
SCIENTIFIC STUDY
COMBINED WITH THE
EXPERIENCE OF MANY
YEARS.
• Vision – Seeing – Visual
• Audition – Hearing – Auditory
• Olfaction – Smelling – Olfactory
• Gustation – Tasting – Gustatory