Learning Goal One: Discuss basic
principles of sensation and perception.
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Cornea Transplants
Over forty thousand cornea transplants are
performed each year.
The odds of rejection of the new cornea are low
because the cornea has a low blood supply.
Abigail was born with congenital glaucoma.
At age 2, she had surgery and the gift of sight.
Sight was a gift from a sight organ donor.
Vision connects us to the world.
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Sensation occurs when a person receives
stimulus energy from the external
environment.
The process of transferring physical energy into
electrochemical energy is called transduction.
Perception occurs when a person organizes and
interprets sensory information in order to give
it meaning.
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Bottom-up processing occurs when the
information from the external environment is
registered and sent up to the brain for
interpretation. Bottom-up processing occurs
with first time information, meaning
information that a person is not familiar with.
Top-down processing occurs with higher levels of
cognitive processing. Top-down processing
occurs with information that a person is
already familiar with.
Is It Top-Down or Bottom-Up? Circle the correct answer.
1.
Susie sets up the VCR to tape her favorite television show.
TOP-DOWN or BOTTOM-UP
2.
Melissa’s mom is showing Rebecca how to make the family favorite of
molasses cookies. She walks Rebecca through the recipe stepbystep.
TOP-DOWN or BOTTOM-UP
3.
Tim decides he is going to start a business of putting bicycles together. He
reads the instructions carefully and follows them very closely.
TOP-DOWN or BOTTOM-UP
4.
It’s been two years and Tim’s bicycle business is doing very well. He can
now go through five to eight bicycles a day without looking at any instructions.
TOP-DOWN or BOTTOM-UP
5.
Jeremy is in his first year of algebra and finds the algebra problems very
confusing. He finds that he needs to keep going back to the textbook and seeing what
steps are next.
TOP-DOWN or BOTTOM-UP
1.
Susie sets up the VCR to tape her favorite television show.
TOP-DOWN or BOTTOM-UP
2.
Melissa’s mom is showing Rebecca how to make the family favorite of
molasses cookies. She walks Rebecca through the recipe stepbystep.
TOP-DOWN or BOTTOM-UP
3.
Tim decides he is going to start a business of putting bicycles together. He
reads the instructions carefully and follows them very closely.
TOP-DOWN or BOTTOM-UP
4.
It’s been two years and Tim’s bicycle business is doing very well. He can
now go through five to eight bicycles a day without looking at any instructions.
TOP-DOWN or BOTTOM-UP
5.
Jeremy is in his first year of algebra and finds the algebra problems very
confusing. He finds that he needs to keep going back to the textbook and seeing
what steps are next.
TOP-DOWN or BOTTOM-UP
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The purpose of perception is to take
information from the outside world and
represent it internally.
From an evolutionary perspective, the purpose
of perception is to adapt to stimuli in order to
survive.
We are adapted to our environment. Predators
have their eyes at the front of their heads and
lunch has their eyes to the side to get away!
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Sensory receptors are cells that detect and transmit
information to sensory nerves in the brain.
Sensory receptors set off action potentials in sensory
neurons, which then carry the information to the central
nervous system.
The sense organs and sensory receptors have three classes
based on the type of energy that is being transmitted.
first is photoreception, which involves the detection of light.
Next is mechanoreception, which is the detection of pressure,
vibrations, and movement perceived as touch, hearing, and
equilibrium.
The third class is chemoreception, which is the detection of
chemical stimuli that is detected as smell and taste.
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On rare occasions senses can become
“confused.” Synaesthesia refers to an experience
in which one sense induces an experience in
another sense. For example, a person might
“see” music.
https://www.youtube.com/watch?v=vEqmN
X8uKlA
Phantom limb pain is another case in which
senses become “confused.” Individuals who
have lost limbs report “feeling” pain in the
limb that no longer exists.
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Psychophysics is the study of linking the physical
properties of stimuli with a person’s experience of
them.
An absolute threshold is the minimum amount of
energy needed for a person to detect something. If
a stimulus falls below the threshold then a person
does not experience it.
Under ideal circumstances, a person’s absolute
thresholds are very low. The problem is that there
is so much noise around people that they cannot
detect half of the stimuli that are confronting them.
Noise is the term given to irrelevant and
competing stimuli.
Absolute Threshold
…the minimum amount of energy an
organism can detect 50% of the time
Noise
…irrelevant and competing stimuli
© 2011 The McGraw-Hill Companies,
Inc.
© 2011 The McGraw-Hill Companies,
Inc.
Difference Thresholds
just noticeable difference (JND)
 how much stimulus change is necessary
for detection?
 JND increases with stimulus magnitude
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Weber’s Law
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two stimuli must differ by a constant
minimum percentage (not a constant
amount) to be perceived as different
© 2011 The McGraw-Hill Companies,
Inc.
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influence of information below the
level of conscious awareness
Vicary: EAT POPCORN
Strahan: thirsty v. non-thirsty words
No drink for 3 hours then after
experiment those that saw the drink
words did in fact drink.
© 2011 The McGraw-Hill Companies,
Inc.
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Signal detection theory focuses on decision making about
stimuli while in the presence of uncertainty. It depends
on the individual and contextual variations such as
fatigue, expectancy, and the urgency of the moment.
Information acquisition refers to the information that is
produced in a brain scan.
Criterion is the basis for making a judgment about the
available information.
In Signal Detection Theory, there are four possible
outcomes: Hit, Miss, False Alarm, and Correct Rejection.
Decision “Did I detect something?”
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information acquisition
criterion (basis/motive for judgment)
Possible Outcomes
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hit
miss
false alarm
correct rejection
© 2011 The McGraw-Hill Companies,
Inc.
© 2011 The McGraw-Hill Companies,
Inc.
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Selective attention involves focusing in on a specific
aspect of an experience while ignoring the others.
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Attention is not only selective, but it is also shiftable, meaning
that a person can be focusing their attention on one thing, but
then switches their attention to something else.
The Stroop effect is an example of automatic attention. A
person attempts to name the colors in which words are
presented, but the words do not state the color of the
meaning of the word. For example, the word red
would be written in the color orange. A person would
have difficulty stating orange when the word is red.
© 2011 The McGraw-Hill Companies,
Inc.
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A perceptual set is the predisposition to perceive
something in a particular way.
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Look at the card example on page 107.
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What is out of place?
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Children who do not have perceptual sets are
more accurate than adults in the text example.
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Sensory adaptation occurs when there is a
change in the responsiveness of the sensory
system based on the average level of
surrounding stimulation.
An example of sensory adaptation is when a
person first jumps into a swimming pool. The
water is cold and shocking, but after being in
the water for a few minutes, the person adapts
to the temperature of the water.
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Is there such a thing as ESP (extrasensory
perception)? Over 50 percent of adults in the United
States believe in ESP, while others believe these
occurrences are simply coincidence.
Despite seventy-five years of research, there is no
evidence that supports the existence of ESP.
However, people in general have difficulties with
“random experiences” and often search for
answers to help them explain unusual events.
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When you are finished reflect on the reading
and discus with those around you how
perceptual sets can be good and bad for
society.
Do expectations influence perception?
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Harmless objects or deadly weapons?
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Ethnicity and perceptual errors
…reactions influenced not by personal
prejudice but by knowledge of cultural
stereotypes
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Does practice reduce ethnic bias?
© 2011 The McGraw-Hill Companies,
Inc.