1 how do we sense things? sense receptors are cells located in the sense organs (eyes, ears, etc.)...
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HOW do we Sense Things?SENSE RECEPTORS are cells located
in the sense organs (eyes, ears, etc.) that convert _______________ energy to ______________ energy
SENSE RECEPTORS▼
SENSORY NEURONS▼
BRAIN CELLS
I’m not the only one who has electrical currents running through my body!
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Your brain interprets info. in 2 different ways
1) _____________________ your sense organs (eyes, ears, nose, etc.) send impulses along designated nerve pathways to specific parts of the brain.
► Tells the various senses apart!
EXAMPLE: Eye info. goes to the visual cortex
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2) _____________________ rely on the fact that sensory neurons fire, or are inhibited from firing, only when presented with specific stimuli.
► Tells the difference between
sensations WITHIN a
particular sense!
EXAMPLE: Color vs. Shape
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What do you think might happen if your sensory neurons sent information to
the wrong part of the brain?
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WEIRD, but TRUE!• _______________: A rare condition in
which stimulation of one sense also evokes a sensation in anotherIn other words, a person might see sounds or smell
colors
EXAMPLE 1: A person may say that the aroma of cinnamon feels like velvet
EXAMPLE 2: One might say that the sound of a clarinet tastes like cherries.
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Sensing the World:Some Basic Principles
Threshold Absolute Threshold
Difference Threshold
Subliminal Stimulation
Signal Detection Theory
Sensory Adaptation
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THRESHOLDS
1) ________________________:
The smallest quantity of physical energy
that can be reliably detected by an observer
RELIABLE = Detection _____ of the time
EXAMPLE:What’s the smallest line you will
read correctly 50% of the time?
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No
Detection
Intensity
AbsoluteThreshold
Detected
YesYesNo No
Observer’s Response
Tell when you (the observer) detect the light.
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Thresholds
Absolute Threshold: Minimum stimulation needed to detect one particular stimulus 50% of the time.
Pro
port
ion
of
“Yes”
Resp
on
ses
0.0
0
0
.50
1.0
0
0 5 10 15 20 25 Stimulus Intensity (lumens)
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NORMAL SENSORY ABILITIESVISION: A candle flame on a clear, dark night
from _____ miles away.
HEARING: A ticking watch in perfectly quiet room
from _____ feet away
TASTE: A teaspoon of sugar diluted in _____gallons of water
SMELL: A drop of perfume diffused through a ____-room apartment
TOUCH: Feel the wing of a bee falling in yourcheek from a height of ______
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THRESHOLDS
2) _________________________:
The smallest difference in stimulation that can be reliably detected when comparing two things
A.K.A. Just Noticeable Difference
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Difference Threshold
Difference Threshold: Minimum difference between two stimuli required for
detection 50% of the time, also called just noticeable difference (JND).
DifferenceThreshold
Tell when you (observer) detect a difference in the light.
No
Observer’s Response
No Yes
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Weber’s Law
Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as
different.
StimulusConstant
%
Light 8%
Weight 2%
Tone .3%
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DIFFERENCE THRESHOLD
• When comparing 2 objects, A and B, the difference threshold will depend on the intensity or size of A.
– The larger or more intense A is, the greater the change must be before you can detect a difference.
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DIFFERENCE THRESHOLD EXAMPLE
• In comparing 2 pebbles, you might be able to detect a difference of only a fraction of an ounce
• In comparing 2 massive boulders, such a subtle difference would most likely not be noticed.
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How did Scientists figure this out?......Psychophysics
A study of the relationship between physical characteristics of stimuli and
our psychological experience with them.
Physical WorldPsychological
World
Light Brightness
Sound Volume
Pressure Weight
Sugar Sweet
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Signal Detection Theory (SDT): highlights the limitations of measuring absolute and
difference thresholds
Signal Detection Theory (SDT): Predicts how and when we detect the presence of a faint
stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no
single absolute threshold and detection depends on: Person’s
experienceExpectationsMotivationLevel of fatigue
Carol L
ee/ Tony Stone Im
ages
___________________: some ___________________: some people are habitual yea-sayers people are habitual yea-sayers and others are habitual and others are habitual naysayers which can greatly naysayers which can greatly affect and disrupt data affect and disrupt data collection techniques.collection techniques.
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SDT Matrix
Decision
Yes No
Signal
Present Hit Miss or False Negative
AbsentFalse
Alarm or False Positive
Correct Rejection
The observer decides whether she hears the tone or not, based on the signal being present or not. This translates into four
outcomes.
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Subliminal Threshold
Subliminal Threshold: When stimuli are below
one’s absolute threshold for conscious
awareness.
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SUBLIMINAL ORIGINS• 1950s
• Movie theater owner claimed to sell more refreshments when he flashed the words “EAT MORE POPCORN” or “DRINK COKE” for a split second on the screen.
• Turned out to be a hoax
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SUBLIMINAL MESSAGES
• Subliminal messages have appeared in all kinds of places:
– Magazines– Movies– Political Campaigns– Weight Loss Strategies– Self-Improvement Books– Memory Enhancers and Study Aids
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SELF-HELP SUBLIMINAL TAPES
• Many promise to help you stop smoking, lose weight, relieve stress, or stop taking drugs
• Study = Placebo tapes vs. “Real Tapes”
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The Effect of Subliminal Stimuli • “Absolute” threshold is merely the point at which
we detect a stimulus half the time. Therefore it is possible to sense subliminal (below threshold) stimuli.
• Laboratory research reveals that subliminal stimuli has a subtle, fleeting effect that may prime (or heighten) a feeling that already exists.
• Research in subliminal priming confirms that much of our information processing occurs automatically without detection by our conscious mind and supports evidence in the powers of intuition.
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Sensory Adaptation
Diminished sensitivity as a consequence of constant stimulation.
Put a band aid on your arm and after awhileyou don’t sense it.