Transcript Sensation - Cayuga Community College

Sensation & Perception
Chapter 5
Sensing & Perceiving Information
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Sensation: Receiving
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Perception: Organizing &
Interpreting
Vision – The Eye
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Light enters eye through the cornea
Passes through the pupil and lens
Focused into an image on the retina
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Retina
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Light sensitive inner surface of the eye
Contains Rods & Cones
Receptor cells convert light to neural impulses and
send to brain
Brain reassembles impulses into an image
Vision – The Eye
Vision – Retina Receptors
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Rods
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detect black, white, and gray
necessary for peripheral and twilight vision
Cones
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concentrated near the center of retina
function in daylight or well-lit conditions
detect fine detail
color vision
Vision--Receptors
Receptors in the Human Eye
Cones
Rods
Number
6 million
120 million
Location in
retina
Center
Periphery
Sensitivity in
dim light
Low
High
Color sensitive?
Yes
No
The Eye
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Optic Nerve: nerve that carries neural
impulses from the eye to the brain
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Blind Spot: point at which the optic
nerve leaves the eye
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No receptor cells
creates a “blind spot”
Vision – Feature Detection
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Feature Detectors
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nerve cells that respond to specific features
of a stimulus
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shape, angle, or movement
fMRI can be used to determine what object
a person is looking at
Visual Information
Processing
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Parallel Processing
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processing many parts of a problem all at
once
the brain’s natural mode of information
processing for many functions (including
vision)
Visual Information Processing
Abstraction:
Brain’s higher-level cells
respond to combined
information from
feature-detector cells
Feature detection:
Brain’s detector cells
respond to elementary
features-bars, edges, or
gradients of light
Retinal processing:
Receptor rods and
conesbipolar cells
 ganglion cells
Recognition:
Brain matches the
constructed image with
stored images
Scene
Color-Deficient Vision
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People who suffer redgreen blindness have
trouble perceiving the
number within the
design
Color Vision
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Young-Helmholtz trichromatic (three-color)
theory
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retina has 3 different color receptors (red, green,
blue)
different combinations allow for the perception of
any color
Opponent-process theory
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opposing processes of retina enable color vision
e.g., some neurons are turned on by red and off
by green
Audition
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Audition- the sense of hearing
Frequency- the number of complete
wavelengths that pass a point in a given time
Pitch- a tone’s highness or lowness
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depends on frequency
long sound waves = low frequency & low pitch
short sound waves = high frequency & high pitch
Audition--The Ear
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Sound waves
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auditory canal eardrum (vibrates with the
waves) middle ear cochlea (in inner ear) 
triggers neural impulses (auditory nerve) 
thalamus  auditory cortex (temporal lobe)
Middle Ear
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chamber between the eardrum and cochlea
contains 3 tiny bones (hammer, anvil, stirrup)
that transmit vibrations to the cochlea
Audition--The Ear
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Inner Ear
innermost part of ear
 Contains the Cochlea
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a fluid-filled tube through which sound
waves trigger nerve impulses
Decibel Levels - Common Sounds
Locating Sounds
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sound reaches one
ear more intensely
and more quickly
auditory system is
able to detect tiny
differences
hearing loss in one
ear = difficulty
locating sounds
Touch
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Skin Sensations
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pressure
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only skin sensation with identifiable
receptors
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warmth
cold
pain
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Rubber hand illusion
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http://www.youtube.com/watch?v=TCQbygjG0RU
Pain
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No theory explains all available findings
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Gate-Control Theory (1960s)
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provides a useful model for understanding pain
the spinal cord contains small fibers (conduct pain
signals) and large fibers (conduct other sensory
signals)
“gate” opened by the activity of pain signals
traveling up small nerve fibers
“gate” closed by activity in larger fibers or by
information coming from the brain
Pain Control
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Massaging area next to pain
Distraction
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Diverting the brain’s attention may bring relief
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Pleasant imagery
Count backward
Virtual reality
Taste
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Taste Sensations
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sweet
sour
salty
bitter
savory (umami)
Taste
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Taste receptors
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reproduce themselves every 2 weeks
taste sensitivity and # of taste buds decrease as
we age
Sensory Interaction
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one sense may influence another sense
the smell of food influences its taste
smell + texture = flavor
rubber hand illusion (vision & touch interact)
Smell
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humans can detect 10,000 odors
olfactory receptor cells
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respond to aromas
messages sent through receptor axons to the
olfactory bulb in the brain
messages then travel from olfactory bulb to
temporal lobe & limbic system
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odors can evoke memories
Smell
Body Position and Movement
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Sixth sense
Kinesthesis
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the system for sensing the position and
movement of individual body parts
interacts with vision
Vestibular sense
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monitors head and body position to maintain
balance
fluid in the inner ear moves when head moves
messages are sent to the cerebellum
Perceptual Organization
- organizing & interpreting info from senses
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Gestalt
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an organized whole
tendency to
integrate pieces of
information into
meaningful wholes
Necker cube
Perceptual Organization
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First: Need to
discriminate objects
from backgrounds
Figure and Ground
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perceiving an object
(figure) as distinct from its
surroundings (ground)
In a busy restaurant:
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voice you attend to = figure
all other voices = ground
Perceptual Organization- Gestalt
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Next step: Need to organize the figure into a
meaningful form
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Grouping
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the tendency to organize stimuli into meaningful
groups
grouping rules identified by Gestalt psychologists
the “whole” that we perceive differs from the sum
of its parts
Perceptual Organization- Gestalt
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Grouping Rules
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proximity - we group nearby figures together
similarity - we group similar figures together
continuity – we perceive continuous patterns
closure – we fill in gaps to create complete objects
connectedness - spots, lines, and areas are seen
as a unit when connected
Perceptual Organization- Gestalt
Proximity
Similarity
Continuity
Closure
Connectedness
Perceptual Organization-Depth
Perception
Visual Cliff
Perceptual Organization
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Depth Perception
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seeing objects in three dimensions
allows us to estimate distance
Visual Cliff
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laboratory technique used to test depth
perception
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http://www.youtube.com/watch?v=eyxMq11xWzM
Perceptual Organization
Depth Perception
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Binocular cues –
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depth cues
depend on use of two eyes
retinal disparity
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images from the two eyes differ
brain compares the images to compute
distance
the larger the difference, the closer the object
Perceptual Organization
Depth Perception
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Monocular Cues
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depth cues needed for objects at further distances
available to each eye separately
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relative height
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higher objects seen as more distant
relative size
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smaller image is more distant
Depth Perception
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Monocular Cues
(continued)
 interposition
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if one object blocks our
view of another, we
perceive that object to
be closer
Depth Perception
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Monocular Cues (continued)
 relative clarity
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relative motion
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hazy object seen as more distant
as we move, stable objects appear to also move
fix gaze on object: those beyond appear to move
with you; those in front appear to move backward
relative brightness
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dimmer objects seem farther away
Depth Perception
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Monocular Cues
(continued)
 linear perspective
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parallel lines appear
to converge with
distance
Perceptual Constancy
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perceiving objects as
unchanging despite changes in
illumination and retinal image
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able to recognize objects despite
changes in color, shape, & size
Shape Constancy
Shape constancy – as a door opens the shape
projected on retina looks more like a trapezoid…but
we still perceive it as rectangular.
Perceptual Constancy
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Color depends on context
Color Constancy
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we perceive familiar objects as having
consistent color
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even if illumination changes and alters the
wavelengths reflected by the object
Perceptual Organization
Size-Distance Relationship
Perceptual Organization- SizeDistance Relationship
Depth Perception
Perceptual Organization
Müller-Lyer Illusion
Perceptual Organization
Brightness Contrast
Perceptual Interpretation
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Perceptual Adaptation
 (vision) ability to adjust to an
artificially displaced visual field
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glasses that invert view of the world (looks
upside down)
humans can adapt relatively quickly and learn
to coordinate movements accurately
Perceptual Interpretation
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Perceptual Set
 a mental predisposition to perceive
one thing and not another
 our experiences and expectations
influence what we perceive
Perceptual Set – context effect
Is There Extrasensory
Perception?
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Parapsychology
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the study of paranormal phenomena
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Astrological predictions
Psychic healing
ESP
Psychokinesis (“mind over matter”; levitating)
Is There ESP?
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Extrasensory Perception (ESP)
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controversial claim that perception can occur
apart from sensory input
types of ESP:
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Telepathy (mind-to-mind communication)
Clairvoyance (sensing remote events)
Precognition (perceiving future events)