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Psychology 1000 Lecture Notes - Absolute Threshold, Chemoreceptor, Barbiturate

Course Code
PSYCH 1000
Terry Biggs

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Psychology 10/26/2010 10:20:00 AM
even though people have many shared experiences, ever individual has their
own reality
The process by which our sense organs respond to and translate
stimuli into nerve impulses sent to the brain
Organizing the stimulus input and giving it meaning
Stages of sensation and perception
Stimuli activate sensory receptors
Sensory receptors translate information into nerve impulses
Specialized neurons analyze stimuli features
Stimulus pieces are reconstructed and compared to stimuli (stored
records) in memory “pattern recognition”
Perception is then consciously experienced *only once the
previous four have been accomplish*
Stimulus Detection
Absolute limits (lymen) of sensitivity
o Dimmest light in which we can see objects
o Softest sound we can hear
Recognizing differences between stimuli
o Smallest difference in brightness detectable
o Recognizing differences between tones
The Absolute Threshold
o The lowest intensity at which a stimulus can be detected 50%
of the time when your odds at detecting stimulus is 50-50
o However, the environment contains a background level of
stimulation for each sense and this level (the ADAPTATION
level) must be overcome if a stimuli is to be detected
o At 100% hearing the stimulus is reported 100% of the time

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The amount of energy required to overcome the Adaptation level is
o it is subject to variation with changes in circumstances
Locke’s experiment : fill one bowl with hot water, one with cold and
one with room temp water
o Put one hand in hot and one in cold
o Hands will adapt
o Hot and cold water will not feel as hot/cold
o Therefore both hands are being differential adapted to
o If both hands are put in room temp water, cold hand will say
water is hot, while hot hand will say water is cold you are
getting two different message about same water because you
adapted to earlier bowls with different temperatures
Signal Detection Theory:
Decision criterion: A personal standard of certainty before a person
will say that they detect a stimulus
The decision criterion is affected by:
o Conservativeness or boldness
Bold subjects show high Hits & High False alarms

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Conservative subjects show high misses and Correct
o Increasing rewards for hits or costs for misses
However, Criterions can be manipulated by changing
the payoff for each cell of the response matrix by
changing the payoffs people will change perception due
to risk of saying yes or no
**This shows perception is, to some extent, a decision
Subliminal Perception:
A subliminal stimulus cannot be perceived consciously but do
register in the nervous system
o the synapse makes subliminal perception possible (your
system collects information even though you do not perceive
o (subliminal messaging/advertisment in movies)
Stimuli above threshold influence behaviour much more than
subliminal stimuli
Subliminal stimuli have stronger effects on attitudes
o E.g. tips at restaurants up to 25% more
Effects may be due to placebo effects
JND/The difference threshold (just noticeable difference or JND)
the smallest difference between two stimuli that people can
perceive 50% of the time
Weber’s Law
The smaller the fraction the less change is necessary to produce a
o Thus only a 2% change is necessary to detect a difference in
lifted weights.
o Compared to a 33% change necessary for a change in the
taste of salt to be noticed
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