Transcript Sensation and Perception

Sensation and Perception
Unit 3
Chapter 4
Students will explain the processes of sensation and perception and describe the interaction between
the person and the environment to determine determining perception
Basic Concepts
sensation- stimulation of sense organs
– converted into neural impulses
perception- selection, organization, and
interpretation of sensory input
– meaningful experiences
psychophysics- study of how physical
stimuli are translated into psychological
experiences
P.23 Examine the processes of sensation and perception and elaborate on how they interact.
Thresholds: Looking for Limits
thresholds- dividing point between energy
levels that do and do not have a
detectable effect
– absolute threshold: minimum stimulus
intensity detected
– just noticeable difference: smallest difference
in stimulus intensity that a specific sense can
detect
P.24 Explain the concepts of threshold
and adaptation
Examples of Absolute Thresholds
Sense
Absolute Threshold
Vision
A candle flame seen at 30 miles on a dark clear night
Hearing
The tick of a watch under quiet conditions at 20 feet
Taste
One teaspoon of sugar in two gallons of water
Smell
One drop of perfume diffused into entire volume of a six
room apartment
Touch
The wing of a fly falling on your cheek from a distance of 1
centimeter
P.24 Explain the concepts of threshold
and adaptation
Signal Detection Theory
proposes that detection of stimuli involves
decision processes as well as sensory
processes, both influenced by variety of
factors besides stimulus intensity
– expectations
– level of “noise”
Perception Without Awareness
subliminal perception- registration of
sensory input without conscious
awareness
– below threshold
– money, sex,
religion
Sensory Adaptation
gradual decline in sensitivity to prolonged
stimulation
continued exposure = adaptation to
stimulus
automatic process that keeps people
tuned into changes rather than constants
in their sensory input
Our Sense of Sight: The
Visual System
Unit 3
P.26 Describe the visual, sensory and
auditory sensory systems.
The Stimulus: Light
light- form of electromagnetic radiation that
travels as a wave
– Varies in both amplitude and wavelength
Amplitude affects perception of brightness
Wavelength affects perception of color
P.25 List forms of physical energy for which humans and nonhuman animals do and do not have sensory receptors.
The Eye: A Living Optical
Instrument
cornea- provides 2/3
of eyes total power
lens- focuses light
rays on the retina
retina- absorbs light,
processes images,
sends visual info to
brain
pupil- permits light to
pass into eye
P.26 Describe the visual, sensory and auditory sensory systems.
Visual Receptors: Rods and Cones
RODS
100-125 million rods
night vision and
peripheral vision
sensitive to dim light
CONES
5-6.4 million cones
daylight vision and
color vision
visual acuitysharpness and
precise detail
P.26 Describe the visual, sensory and
auditory sensory systems.
Visual Deficiencies
Nearsightedness
close objects seen
clearly but distant
objects appear blurry
light falls short of
retina
eyeball is too long
Farsightedness
distant objects seen
clearly but close
objects appear blurry
light falls behind
retina
eyeball is too short
P.26 Describe the visual, sensory and auditory sensory systems.
Visual Adaptation
Dark Adaptation
process by which the
eyes become more
sensitive to light in
low illumination
Complete in 30
minutes
Light Adaptation
process whereby
eyes become less
sensitive to light in
high illumination
Improves visual acuity
Viewing the World in Color
trichromatic theory- human eye has three
types of receptors with differing
sensitivities to different light wavelengths
– red, green and blue
– “color mixing” allows for all colors
afterimage- visual image that persists after
a stimulus is removed
– color will be complement of original color
https://www.youtube.com/watch?v=dxqsBk7Wn-Y
Perceiving Forms, Patterns,
and Objects
Unit 3
Perceptions are Subjective
same visual input can result in radically
different perceptions
perceptual set- readiness to perceive a
stimulus is a particular way
inattentional blindness- involves failure to
see visible objects or events because
attention is focused elsewhere
Looking at the Whole Picture:
Gestalt Principles
Figure and Ground
figure is thing being
looked at, while
ground is background
against which it
stands
figures appear closer,
stand out and have
more substance
P.28 Explain Gestalt’s principles of
perception.
P.28 Explain Gestalt’s principles of
perception.
Gestalt Principles
Proximity
things that are near
one another seem to
belong together
P.28 Explain Gestalt’s principles of perception.
Gestalt Principles
Closure
group elements to
create completeness
fill in gaps
P.28 Explain Gestalt’s principles of
perception.
Gestalt Principles
Similarity
tendency to group
stimuli that are similar
same characteristics
P.28 Explain Gestalt’s principles of
perception.
Gestalt Principles
Simplicity
Tendency to group
elements that
combine to form a
good figure
Organize forms in
simplest way possible
P.28 Explain Gestalt’s principles of
perception.
Gestalt Principles
Continuity
follows in direction led
connect points that
result in straight or
gently curved lines
that create “smooth”
paths
P.28 Explain Gestalt’s principles of
perception.
Perceiving Depth of Distance
depth perception- interpretation of visual cues
that indicate how near or far away objects are
Binocular Cues
clues about distance based on
differing views of the two eyes
retinal disparity- images
projected to different locations
on right and left retinas
convergence- sensing the
eyes converging toward each
other as they focus on closer
objects
Monocular Cues
clues about distance based on
the image in either eye alone
motion parallax- images
projected at different distances
moving across retina at
different rates
pictorial depth cuesclues about distance
given in a flat picture
P.29 Describe binocular and monocular depth cues.
Phi Phenomenon
• illusion of movement created by
presenting visual stimuli in rapid
succession
• our perceptions fill in the gaps to perceive
motion
Stroboscopic Photography
Our Sense of Hearing:
The Auditory System
The Stimulus: Sound
sound waves are vibrations of molecules
that travel through physical medium
– wavelength described in terms of frequency
cycles per second, hertz (Hz)
– amplitude described in terms of loudness
measured in decibels (dB)
Sensory Processing in the Ear
external ear
– vibration of air
molecules
middle ear
– vibration of movable
bones
inner ear
– waves in a fluid
https://www.youtube.com/watch?v=flIAxGsV1q0
The human ear
pinna- sound
collecting bone
hammer, anvil,
stirrup- amplify tiny
changes in air
pressure
cochlea- contains
receptors for hearing
Our Chemical Senses:
Taste and Smell
https://www.youtube.com/watch?v=EJud8MKrvBE
Taste: The Gustatory System
Chemical substances that are soluble
Receptors are clusters of taste cells on
taste buds
– short life of 10 days
– perception depend on patterns from receptors
Four primary tastes
– sweet, sour, salty, bitter
https://www.youtube.com/watch?v=kyrIxAXZISc
Smell: The Olfactory System
chemical substances-volatile ones that
evaporate and spread throughout the air
– dissolved in fluid, mucus in the nose
olfactory cilia- hairlike structures in upper
portion of nasal passages
– short life (30-60 days)
Sensory adaptation = 4 minutes
Our Sense of Touch
conversion of physical sensation into a
psychological experience
mechanical, thermal and chemical energy
– pressure of touch in warmth, cold and pain
P.27 Describe other sensory systems, including olfaction and gustation, and identify skin senses, kinesthesis, and vestibular
sense.
Puzzles in Pain Perception
Pain Pathways
1. Fast- registers
localized pain and
relays it to cortex in
fraction of a second
2. Slow- conveys
longer lasting,
aching or burning
pain that comes
after initial injury
https://www.youtube.com/watch?v=1mHIv5ToMTM
Gate Control Theory
Incoming pain
sensations must pass
through “gate” in
spinal cord that can
be closed, blocking
ascending pain
signals
Cognitive and
emotional processes
block pain signals
Our Other Systems
Kinesthetic
monitors positions of
various body parts
receptors located in joints
and muscles
Vestibular
responds to gravity and
keeps you informed
about you body’s
location in space
provides the sense of
balance and equilibrium
receptors located within
semicircular canals of
ear
P.27 Describe other sensory systems, including olfaction and gustation, and identify skin senses, kinesthesis, and
vestibular sense.