Transcript Sensation and Perception

Sensation and Perception
• “Everything you see or hear or experience in
any way at all is specific to you. You create a
universe by perceiving it, so everything in the
universe you perceive is specific to you.” –
Douglas Adams
Sensation
•The process of
taking in
information from
the environment
Transduction
• The process of changing raw
sensory data into an
electrochemical message that
will be sent to the brain for
interpretation.
Perception
•How we recognize,
interpret, and organize
our sensations
• Input comes primarily from these
five external senses:
–Visual (Eyes)
–Audio (Ears)
–Cutaneous/Tactile (Touch)
–Olfaction (Smell) (Nose)
–Gustation (Taste) (Tongue)
Kinesthetic Sense
• The kinesthetic sense
monitors the position and
movements of muscles,
bones, and joints.
Receptors in the joints
and tendons send the
brain information about
the angle of your limbs.
Vestibular Sense
• The system for
balance.
• Fluid in the
semicircle canals of
the inner-ear
maintain the body’s
sense of balance.
Detection Threshold or Absolute Threshold
•The minimum intensity
of energy required to
produce sensation in a
receptor cell at least
50% of the time
Difference Threshold or
Just Noticeable Difference
•The smallest change
in stimulation that
you can detect
Weber’s Law
• The greater the magnitude of the
stimulus, the larger the difference must
be in order to be noticed
–IE. If you are carrying 20 lbs. and add 5
lbs., it’s noticeable. If you are carrying 100
pounds and add 5 pounds, it may not be
noticeable. You may need to add 20 lbs. to
100 pounds to make it noticeable.
Sensory Adaptation
• Diminished sensitivity as a result of
constant and unchanging stimulation.
• You jump into a swimming pool of cold
water, but eventually you “get used to
it”. Or, you wear your glasses so often
that you sometimes forget that they
are on.
Subliminal Perception
• Thresholds imply that there must be
stimulus below and beyond our
current levels of detection. Can
human behavior be influenced by
stimulus that is below or beyond our
level of awareness?
Subliminal Perception
Extrasensory Perception
• Some people claim to have extra
powers of perception, or the ability
to respond to an unknown event that
is not presented to any of the known
senses.
• Parapsychology
Examples of
Extrasensory Perception
• Telepathy: Transfer of information on thoughts
or feelings between individuals by means
other than the five classical senses
• Precognition: Perception of information about
future places or events before they occur.
• Clairvoyance: Obtaining information about
places or events at remote locations, by means
unknown to current science.
• Does ESP Exist?
• Remote Viewing?
• Telepathy?
Paranormal Activity
• A&E Series Paranormal State
• A&E Series Psychic Kids
Visual Sensation
• How Do We See?
• Visual Sensation and Perception
• Vision And Behavior
Human Eyeball
Cornea
• transparent protective coating over the
front part of the eye
Iris
• the colored part of the eye – this muscle
dilates or contracts the pupil to allow more
or less light to enter
Pupil
• the small, adjustable center of
the iris that allows light to
enter the eye
Lens
• flexible enough to focus on objects near or far
(accommodation) – if an object is very close is
gets smaller and rounder; if an object is
further away, it get larger and wider
Retina
• The inner lining of the back of the eyeball.
The lens focuses an image from the
outside world on the retina, and the retina
in turn transduces the image.
Fovea
• On the retina, directly behind the lens.
The area of sharpest picture.
• Acuity – the sharpness of vision
• Nearsightedness – the misshapen eyeball
focuses light rays in front of the retina –
you will see near objects well, but not far
away objects
• Farsightedness – the light rays from
nearby objects reach the retina before
they have been focused – you will see far
objects better than near objects
Rods and Cones
• In the retina. Rods determine shades of
light and dark and detect motion. Cones
determine color.
Optic Nerve
• Carries the transduced visual information from
the eye and sends it to the brain for processing.
Blind Spot
• The area closest to the optic nerve, that has no
receptor cells. Also known as the optic disc.
Optic Chiasm
• The point in the brain at which
messages from the visual fields are
split to the appropriate areas of the
brain
–Prosopagonosia - stroke victim
disorder in which victims cannot
recognize faces, but can still see well
and recognize emotions on faces
Stereopsis (Contralateral Shift)
Color Vision
• There are two theories of color
vision:
–Trichromatic Theory
–Opponent-Process Theory
Young-Helmholtz Theory
Trichromatic Theory
• Rods and cones are pre-set to
be sensitive to RED, GREEN,
and BLUE. All of the colors
that we see are combinations
of those three colors.
All other colors can be derived by combining these three.
Opponent-Process Theory
• Sensory receptors in the
retina come in pairs:
–Red/Green
–Yellow/Blue
–Black/White
Opponent-Process Theory
• If one sensor is stimulated, the other is
inhibited
• If one sensor is over-stimulated, and fatigues,
the paired sensor will be activated, causing an
afterimage
• If a person is missing a particular pair of
sensors, they will be colorblind to those hues
– Dichromatic Color Blindness have difficulty seeing
shades of red and green, or yellow and blue
• Hue – the color that we see is
determined by the wavelength (the
distance from one wave peak to the next)
of the light wave that the eye is receiving
• Brightness is influenced by the
height of the waves (amplitude) of
light that are received by the eye
• The shorter the wavelength, more
bluish colors
• The longer the wavelength, more
reddish colors
• The higher the wave, more yellowish
• The lower the wave, more greenish
Color Range
Visual Perception
• Magic Fools The Eye
The Visual Cliff
Figure/Ground Dynamic
• The ability to distinguish different
objects from one another
• Analyzing separate information
allows us to re-act to each individual
object accordingly
–Camouflage – when figures blend into
the background
Figure-Ground Dynamic
Camouflage
Gestalt Rules
–Gestalt Psychologists focused on how
we normally perceive images as
groups, not isolated elements
–Several factors influence how we will
group objects:
• Proximity
• Similarity
• Continuity
• Closure
Proximity
• When objects are close
together we tend to
perceive them as together
rather than separate
Proximity
Similarity
• Objects that are similar in
appearance are more likely
to be perceived as
belonging in the same
group
Similarity
Closure
• The tendency to overlook
incompleteness, and
tocomplete objects so that
they fit into our mental
preconceptions of what
objects are supposed to look
like
Closure
Continuity
• To perceive lines and
motion in fluid forms
rather than jagged motions
Continuation
Constancy
• Despite changes in distance or
lighting, objects still maintain
their original properties
–Size Constancy
–Shape Constancy
–Brightness Constancy
Size Constancy
• Objects closer to us will produce bigger
images on our retinas, and as they move
away they project a smaller image. The
actual size of the object does not change.
– IE. When a man is right in front of us, he is 6
ft. tall. As he walk further and further away,
his image gets smaller. He hasn’t shrunk; he
is still 6 ft. tall.
Size Constancy
Shape Constancy
• Objects viewed from different angles will
produce different shapes on our retina.
Though we may change our position, the
shape doesn’t change.
– IE. Looking at the top of a glass one way
makes it look round; from another angle it
looks elliptical. The actual shape hasn’t
changed…it is still round.
Brightness Constancy
• We perceive objects as having a
constant color, despite lighting,
shading, etc.
–A brick wall is still red, whether bright
sunlight is on it, or darkness has made
it look gray.
Depth Cues
• Depth Cues allow us to perceive the
world in three dimensions.
– Monocular Cues are depth cues that do not
depend on having two eyes working in
conjunction together
– Binocular Cues are depth cues that depend
on having two eyes working in conjunction
with each other
Monocular Cues
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Linear Perspective
Relative Size
Interposition
Texture Gradient
Shadowing
Motion Parallax
Linear Perspective
• Parallel lines seem to converge the
further they get from us. The gradual
reduction of image size as distance from
the object increases
• Vanishing Point – where two parallel lines
connect in the distance
Relative Size
• Objects that project a smaller
image on the retina are
perceived as further away;
larger images are closer
Elevation
• Objects on top of our horizon
are smaller and further away,
objects below are closer and
larger
Interposition
• Near objects partially
obscure objects further
away
Texture Gradient
• Patterns of distribution tend to
grow more dense with
distance – things further away
seem more smooth, up close
more detailed
Shadowing
•Lighted objects seem
closer, darker further
away
Motion Parallax
• As images move across the
retina, the perception of
movement is created. Objects
further away move slower across
the retina, closer objects move
faster.
Binocular Cues
•Binocular
Disparity/Retinal
Disparity
•Convergence
Binocular Disparity
• Each of our eyes sees an object from
a slightly different angle and projects
that image onto the retina. The
closer an object is, the further apart
the two retinal images are. Further,
closer images.
Convergence
• As objects get closer and
further from us, our eyes
move towards each other or
away. The closer they are, the
closer the object.