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Lecture 11

PSYA01H3 Lecture Notes - Lecture 11: False Alarm, Optometry, Subliminal Stimuli


Department
Psychology
Course Code
PSYA01H3
Professor
Steve Joordens
Lecture
11

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Lecture 11: Sensation and Perception: Subliminal Perception
-Recall: Weber is the one who recognized just noticeable differences (JND) (e.g. of JND,
optometrist doing a vision test for an individual)
Perceptual thresholds
-a threshold is a structure, an entryway, changes
how much energy or power does a stimulus have to be until we feel it?
-the asolute threshold is he e a’t detet it, ad he e just detet it
-a challenge to find absolute threshold
-subliminal perceptions work by placing a message that our conscious mind could not detect
udereath a piee of edia, therefore aipulatig a idiidual’s thoughts
-can the brain detect messages that our conscious mind cannot?
-advertisers do many subliminal messages
-it is unclear if it works, but advertisers do place messages that the eye usually cannot detect,
hoping it works
-experimental context: we would see distinct trials and the stimulus may or may not be there,
partiipats ay say soethig is there ee he there is’t, they ed up guessing
(sometimes they are right)
-possible results of the experiment:
correct rejection: when there is no stimulus and the participant says no
Hit: when there is a stimulus and the participant says yes
Miss: when there is a stimulus and the participant says no
False alarm: when there is no stimulus and the participant says yes
Signal detection theory
-bias can occur when the participant is more likely to say yes, which means they will have high
hits and false alarm
-another type of bias is when the participant says no very often, and only say yes when they are
very sure of a stimulus being there; results in low hits and false alarms
-this causes it to be hard to determine absolute threshold, due to bias
-however, e a aipulate a perso’s ias
-for example, start off by giving participant 20 dollars and see how much money they have left
at the end
Scenario 1: giving a participant a dollar each time for a hit and there is no penalty for false
alarms (gets the participant to say yes)
Scenario 2: give a dollar for a hit and lose 50 cents for false alarm
Scenario 3: give 50 cents for hit and lose 50 cents for false alarm (natural bias will occur)
Scenario 4: give 50 cents for hit and lose 1 dollar for false alarm
Scenario 5: no reward for hit and lose 1 dollar for false alarm (gets the participant to say no)
-the logic is that with money (or any reward) we can change how a person responds
-area where to the left of the line that is measuring hits and false alarms (null sensibility line)
would indicate hit rates are higher than false alarms
find more resources at oneclass.com
find more resources at oneclass.com
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