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Lecture 4

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Western University
Psychology 2115A/B

Lecture Four 9/19/2012 1:18:00 PM  No matter what people have bias  When people want the most amount of hits, they put beta directly in the middle where the two curves meet EXAMPLE How do you make someone change there criterion placements?  1. The expectation that there are going to be many signals (tones) o if the experimenter says that 9/10 times there is going to be a stimulus, so if the subject is unsure, they most likely will say that they heard something EXAMPLE o P(i/s) probability of a signal o P(i/N) probability of noise  Motivation: o Pay-off: rewards for right answer, penalties for wrong o Make all the pay-offs different- HIT ($1.00)/ CORRECT REJECTION ($0.05)  When people are unsure they will most likely say they heard something because the pay-off is larger for a hit o Example: miss  If the punishment for a miss is great (-500$) the subject will be very conservative and most likely wont say no o Example: does this patient have cancer? XXX YES NO YES Early diagnosis death NO Extra lab work Done with doctor o Example: find a mate XXX YES NO YES Happy ever after Another one coming… oh well NO Life long agony Good decision Psychophysical Function  There is a physical intensity of a stimulus, when you experience this intensity you have some sort of response to it (weak sound, weak reaction)  Fechner proposed that there must be a relationship between the strength of the stimulus and the strength of the psychological response  Physical = PHY (ϕ), psychological PSY =(ψ)  Equation F(ϕ)=ψ  There is a physical stimulus that gives ride to psychological stimulus and there will be a response  1. Nominal scale o categorizes two or more things, only tells you if two things are equal  2. Ordinal scale o orders of the numbers is meaningful o the differences between the numbers have no meaning  example if a light is given the number one and the other is given the number 5, you know that 5 Is brighter than 1, but you don’t know by how much  3. Interval o preserves intervals of equal quantity o interval properties are meaningful and comparable o example: temperature  the difference between 5 degrees and ten degrees are the same as the difference between 10 degrees and 15 degrees  but 10 degrees is not double the heat of 5 degrees (ratio not calculated)  4. Ratio o preserves ratio relationships o 5 meters is half of 10 meters Logarithms  It’s a function, is a relationship between the first set of scores and the second  Fechner said that the psychophysical function is logarithmic o 1. Log (XY)= log x+y  log (4x2) =
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