Download Sensation and Perception

8/16/2010
Sensation and Perception
Sensation & Perception
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„
The interplay between the external world,
physiological systems
systems, and psychological
experience
How the external world makes “impressions”
on our nervous system & how the nervous
system organizes those impressions
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Working Together
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Sensations: Detect environment and encode
it into neural signals
Perception: Select, organize, and interpret
the sensations that result from these signals
BiDirectional Influence
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Bottom up processing
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I f
Information
ti from
f
the
th senses is
i sentt for
f processing
i
Top down processing
‰
Information from higher levels is sent down and
influences perception of the world
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Sensing the World
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Happens through our senses
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System specific stimuli
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Vision, hearing
Vision
hearing, taste
taste, smell
smell, proprioceptive (touch/
movement)
Each system has a form of energy that it can detect and
process
Physical energy must exceed absolute thresholds (in some
cases must also exceed other thresholds)
Has transduction mechanisms to change physical energy
into neural information then sends to specific brain areas
Can be influenced by attention
Vision
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Eye detects electromagnetic radiation (light)
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Movementt
M
Color
Humans are visual creatures
‰
Light travels quickly, travels in straight lines,
interacts with surfaces in the environment (is
reflected
fl t d or absorbed)
b b d)
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Information to the brain
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Passed to the visual cortex
Processed in a parallel and distributed
manner
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Connections between areas give us a sense of
coherence
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Perceptual Processes
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Identifying everything and documenting it in
detail is a lot of work
work, so your visual system
takes shortcuts
Our expectancies can guide what we see
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Gestalt principles of vision
“the sum is greater than the parts”
Help us quickly identify the nature of the stimuli
Depth Perception
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The environment
provides cues for
perception
The lines tell us
there is depth here
So objects appear
to change size
These linear cues
are often functional
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Size Constancy
We see objects as maintaining their size
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Hearing
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Ear detects sound waves
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Wavelength
W
l
th determines
d t
i
ffrequency and
d pitch
it h off a
sound
Wave amplitude determines the loudness
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0 decibels is the weakest sound detectable by humans
Hearing can be damaged by sounds that are
too loud
lo d and/or listened to for too long
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The auditory system
Passage to the brain
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Information is transmitted via the auditory
nerve
More complex than visual transmission
‰
Most sent to opposite side of the brain, but some
to the same side
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1. Place theory
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Each frequency vibrates a particular place on
the membrane
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High frequency vibrations displace the membrane
close to the oval window
Low frequency vibrations displace the membrane
closer to the tip of the cochlea
We tend to lose the ability to hear high
frequencies first
2. Frequency theory
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Each frequency determines how frequently
the auditory nerve fires
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High frequency = more frequent firing
Low frequency = less frequent firing
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3. Volley Principle
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Clusters of nerve cells can fire in succession
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Even though
g each nerve cell is limited in how
frequently it can fire, multiple cells could fire in
turns
Frequency theory is best for sounds below
1,000
,
times per
p second
Combination of place and frequency is
needed for sounds above 1,000 times per
second
Skin Senses
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Skin is our largest sense system
Responds to mechanical energy from
pressure, temperature, or pain from intense
stimuli
Pain reduction
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Distraction
F
Focused
d breathing
b thi
Counterstimulation
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Chemical Senses
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Taste
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Bumps (papillae) on tongue contain receptors for
taste (taste buds)
Replaced about every 2 weeks
Areas of the tongue more sensitive to salty,
sweet, sour and bitter tastes
Smell
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Top of the nasal cavity contains receptors for
smell
Linked to areas of the brain associated with
feeling and memory
Kinesthetic & Vestibular Senses
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Kinesthetic: movement, posture, orientation
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Embedded in muscle fiber and joints
Si
Signal
l the
h state off muscles
l
Vestibular: balance, movement
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Whether head is moving/tilted
Receptors in semicircular canals of the ear
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The Brain & The Mind
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The brain gives rise to all conceptions of
“mind” - all perceptions & cognitions
Sensory systems pick up energy from the
environment and transduce it to
neurological impulses
These impulses are transferred to the
brain
Where expectations and prior experiences
shape what we perceive
Thus our knowledge of the world is an
interactive process
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