Download Sensation/Perception

Sensation
 Sensation
 a process by which our sensory
receptors and nervous system receive
and represent stimulus energy
 Perception
 a process of organizing and interpreting
sensory information, enabling us to
recognize meaningful objects and
events
Sensation
 Our
sensory
and
perceptual
processes
work
together to
help us
sort out
complext
processes
Sensation
 Bottom-Up Processing
 analysis that begins with the sense receptors
and works up to the brain’s integration of
sensory information
 Top-Down Processing
 information processing guided by higher-level
mental processes
 as when we construct perceptions drawing on
our experience and expectations
Sensation- Basic
Principles
 Psychophysics
 study of the relationship between
physical characteristics of stimuli and
our psychological experience of them
 Light- brightness
 Sound- volume
 Pressure- weight
 Taste- sweetness
Sensation- Thresholds
 Absolute Threshold
 minimum stimulation needed to detect a
particular stimulus 50% of the time
 Difference Threshold
 minimum difference between two stimuli
required for detection 50% of the time
 just noticeable difference (JND)
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
 detection depends partly on person’s
 experience
 expectations
 motivation
 level of fatigue
Sensation- Thresholds
100
Percentage
of correct
detections
 Subliminal
75
50
Subliminal
stimuli
25
0
Low
Absolute
threshold
Intensity of stimulus
Medium
 When stimuli are
below one’s
absolute
threshold for
conscious
awareness
Sensation- Thresholds
 Weber’s Law- to perceive as different,
two stimuli must differ by a constant
minimum percentage
 light intensity- 8%
 weight- 2%
 tone frequency- 0.3%
 Sensory adaptation- diminished
sensitivity as a consequence of constant
stimulation
Vision- Stabilized
Images on the Retina
Vision
 Transduction
 conversion of one form of energy to
another
 in sensation, transforming of stimulus
energies into neural impulses
 Wavelength
 the distance from the peak of one
wave to the peak of the next
Vision
 Hue
 dimension of color determined by
wavelength of light
 Intensity
 amount of energy in a wave
determined by amplitude
 brightness
 loudness
The spectrum of
electromagnetic
energy
Vision- Physical
Properties of Waves
Short wavelength=high frequency
(bluish colors, high-pitched sounds)
Great amplitude
(bright colors, loud sounds)
Long wavelength=low frequency
(reddish colors, low-pitched sounds)
Small amplitude
(dull colors, soft sounds)
Vision
 Pupil- adjustable opening in the
center of the eye
 Iris- a ring of muscle that forms the
colored portion of the eye around the
pupil and controls the size of the
pupil opening
 Lens- transparent structure behind
pupil that changes shape to focus
images on the retina
Vision
Vision
 Accommodation- the process by which
the eye’s lens changes shape to help
focus near or far objects on the retina
 Retina- the light-sensitive inner serface of
the eye, containing receptor rods and
cones plus layers of neurons that begin
the processing of visual information
Vision
 Acuity- the sharpness of vision
 Nearsightedness- condition in which
nearby objects are seen more clearly than
distant objects because distant objects in
front of retina
 Farsightedness- condition in which
faraway objects are seen more clearly
than near objects because the image of
near objects is focused behind retina
Vision
 Normal
Vision
Nearsighted
Vision
Farsighted
Vision
Retina’s Reaction
to Light- Receptors
 Rods
 peripheral retina
 detect black, white and gray
 twilight or low light
 Cones
 near center of retina
 fine detail and color vision
 daylight or well-lit conditions
Retina’s Reaction
to Light
 Optic nerve- nerve that carries neural
impulses from the eye to the brain
 Blind Spot- point at which the optic nerve
leaves the eye, creating a “blind spot”
because there are no receptor cells located
there
 Fovea- central point in the retina, around
which the eye’s cones cluster
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
Pathways from the Eyes
to the Visual Cortex
Visual Information
Processing
 Feature Detectors
 nerve cells in the
brain that
respond to specific
features
 shape
 angle
 movement
Cell’s
responses
Stimulus
How the Brain
Perceives
Illusory Contours
Visual Information
Processing
 Parallel Processing
 simultaneous processing of several
aspects of a problem simultaneously
Visual Information
Processing
 Trichromatic (three color) Theory
 Young and Helmholtz
 three different retinal color receptors
 red
 green
 blue
Color-Deficient Vision
 People who suffer
red-green
blindness have
trouble perceiving
the number within
the design
Visual Information
Processing
Opponent-Process Theory- opposing retinal
processes enable color vision
“ON”
“OFF”
red
green
green
red
blue
yellow
yellow
blue
black
white
white
black
Opponent ProcessAfterimage Effect
Visual Information
Processing
 Color Constancy
 Perceiving familiar objects as having
consistent color, even if changing
illumination alters the wavelengths
reflected by the object
Audition
 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
 depends on frequency
The Intensity of Some
Common Sounds
Audition- The Ear
 Middle Ear
 chamber between eardrum and cochlea
containing three tiny bones (hammer, anvil,
stirrup) that concentrate the vibrations of the
eardrum on the cochlea’s oval window
 Inner Ear
 innermost part of the ear, containing the
cochlea, semicircular canals, and vestibular
sacs
 Cochlea
 coiled, bony, fluid-filled tube in the inner ear
through which
Audition
 Place Theory
 the theory that links the pitch we hear with
the place where the cochlea’s membrane is
stimulated
 Frequency Theory
 the theory that the rate of nerve impulses
traveling up the auditory nerve matches the
frequency of a tone, thus enabling us to
sense its pitch
How We Locate
Sounds
Audition
 Conduction Hearing Loss
 hearing loss caused by damage to the
mechanical system that conducts sound
waves to the cochlea
 Nerve Hearing Loss
 hearing loss caused by damage to the
cochlea’s receptor cells or to the auditory
nerve
Audition
 Older people tend to hear low
frequencies well but suffer hearing loss
for high frequencies
Amplitude required for
perception relative to
20-29 year-old group
1
time
10
times
100
times
1000
times
32
64
128
256
512
1024 2048 4096
8192 16384
Frequency of tone in waves per second
Low
Pitch
High
Touch
 Skin Sensations
 pressure
 only skin
sensation with
identifiable
receptors
 warmth
 cold
 pain
Pain
 Gate-Control Theory
 theory that the spinal cord contains a
neurological “gate” that blocks pain
signals or allows them to pass on to the
brain
 “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
Taste
 Taste Sensations




sweet
sour
salty
bitter
 Sensory Interaction
 the principle that one sense may influence
another
 as when the smell of food influences its taste
Smell
Olfactory
nerve
Olfactory
bulb
Nasal
passage
Receptor cells in
olfactory membrane
Age, Sex and Sense
of Smell
Number
of correct
answers
Women and young adults
have best sense of smell
4
Women
3
Men
2
0
10-19
20-29
30-39
40-49
50-59
60-69
Age Group
70-79
80-89 90-99
Body Position and
Movement
 Kinesthesis
 the system for sensing the position and
movement of individual body parts
 Vestibular Sense
 the sense of body movement and
position
 including the sense of balance
Weber’s Law
Weber’s Constant
Law States That JND = KI
K is the Weber’s constant for a particular
sense.
I is the amount, or intensity, of the stimulus.
Figure 5.5: Length Illusions
Reversible Images
From MIND SIGHTS by Shepard © 1990 by Roger N. Shepard. Used with permission by W. H. Freeman and Company.
Return
Gestalt Principles of Perceptual Grouping
Why Do These Grouping Principles
Guide Perceptual Organization?
Likelihood Principle
Unlikely stimuli and misperceptions
Simplicity Principle
Continue
Impossible Objects
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Perceptual Processing
Top-Down Processing
Bottom-Up Processing
Figure 5.15: Feature
Analysis
Figure 5.17: Recognizing Objects
from Geons
Figure 5.18: Recognition of Objects
With and Without Their Geons
Destroyed
Top-Down Processing
Use knowledge in making inferences to
recognize objects, words, or melodies.
Expectancy and context play an important
role.
Involved in a phenomenon called
pareidolia.
Top-Down Processing
(cont’d.)
Our experiences create schemas.
Schemas can bias our perceptions by
creating a perceptual set.
Predisposition can also be shaped by the
immediate context of the stimulus.
Motivation can affect perception.
Can even influence elements of the
brain’s bottom-up processing.
Network Processing
Object superiority effect and word
superiority effect.
Parallel Distributed Processing (PDP)
Models as explanation for recognition
Example
Figure 5.21: The Object
Superiority Effect
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Linkages: Perception and
Human Development
Habituation and dishabituation used to
study how infants perceive the world.
Newborns can perceive differences among
different black-and-white contrasts.
By three months can discriminate among
blue, green, yellow, and red.
Newborns can perceive differences in the
angles of lines.
Linkages: Perception and Human
Development (cont’d.)
At one month of age, infants
concentrate their gaze on one part
of an object.
By two months, infants
systematically scan the perimeter
of an object.
Infants may be innately tuned to
perceive the human face.
Linkages: Figure 5.24: Infants’
Perceptions of Human Faces
Reprinted from Cognition, vol. 4. M.A. Johnson, S. Dziurawiec, H. Ellis, and J. Morton, "Newborns' Preferential Tracking of Face-Like
Stimuli and Its Subsequent Decline," pp. 1-19, © 1991 with the kind permission of Elsevier Science - NL, Sara Burgerharstraat 25, 1055 KV
Amsterdam, The Netherlands.
Attention
We use attention to:
Direct our sensory and perceptual systems
toward certain stimuli.
Select specific information for further
processing.
Allocate the mental energy required to do
that processing.
Regulate the flow of resources necessary
for performing a task or coordinating several
tasks at once.
Characteristics of
Attention
Improves Mental Processing
Takes Effort
Is Limited
Directing Attention
Voluntary, or goal-directed attention
control reflects top-down processing.
Involuntary attention control reflects
bottom-up processing.
Divided Attention
Sometimes difficult to stop dividing
attention.
Attention is a limited resource.
Easier to do two things at once if one task
is automatic.
Continue
The Stroop Task
Source: Stroop, J.R. (1935). "Studies of Interference in Serial Verbal Reactions." Journal of Experimental
Psychology, 18, 643-662.
Name the color of the INK in which each word is
printed as rapidly as you can Return
Stroop Test
http://www.snre.umich.edu/eplab/demos/st0/stroopdesc.html#The%20Neurophysiology
Although the functions of the
anterior cingulate are very
complex, broadly speaking it acts
as a conduit between lower,
somewhat more impulse-driven
brain regions and higher,
somewhat more thought-driven
behaviors. The Stroop effect's
sensitivity to changes in brain
function may be related to its
association with the anterior
cingulate.
The Stroop Test provides insight
into cognitive effects that are
experienced as a result of
attentional fatigue.
Attention and Automatic
Processing
Efforts to ignore certain stimuli may
create negative priming.
Parallel-processing describes ability to
search for targets rapidly and
automatically.
Applications of Research
on Perception
Aviation Psychology
Human-Computer Interaction
Traffic Safety
Architecture and Interior Design