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Advanced Research Methods PSYC325 Signal Detection Theory with special thanks to Dr. Murray White. Dr. Jan Lauwereyns EA619, ext. 5042 Jan.Lauwereyns@vuw.ac.nz. Lecture notes, available on website http://pavlov.psyc.vuw.ac.nz/325 Brief concepts
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Advanced Research MethodsPSYC325Signal Detection Theorywith special thanks to Dr. Murray White Dr. Jan Lauwereyns EA619, ext. 5042 Jan.Lauwereyns@vuw.ac.nz
Lecture notes, available on website http://pavlov.psyc.vuw.ac.nz/325 • Brief concepts Green, D. M., & Swets, J. A. (1966). Signal Detection Theory and Psychophysics. New York: John Wiley.
Response Stimulus Stimulus – Response Matrix
Response Stimulus Response Stimulus
Special die: three or naught
The special die has to be 0 If the total is 3… The special die has to be 3 If the total is 14… The special die can be either 0 or 3 If the total is 8…
If the total is 6… Special die = 0 Special die = 3
Possible outcomes of each throw You say… The special die is…
> > > > > >
> 7 > 10
> 7 > 10
> 7 > 10 +$120 -$120
Now let’s use a different die: A special die with three faces ‘6’ and three faces ‘0’ instead of three faces ‘3’ and three faces ‘0’
Special die with 3’s and O’s There is no 3 There is a 3 Total of the three dice
Special die with 6’s and O’s There is no 6 There is a 6 Total of the three dice
beta versus d’ • Effects of • signal-to-noise ratio (d’) • decision criteria (beta) • Effects of • perceptual sensitivity • response bias
Effects of Scene Context on Object Perception De Graef, Henderson, Hollingworth There is only a response bias Biederman & co. Context facilitates the perception of congruent objects
Effects of Reward Expectation on Neural Mechanisms of Visual Discrimination
Lauwereyns et al. (2002, Neuron): “wishful seeing” Reward leads to general increase of neural activity = bias effect; no change in d’
Summary • Signal detection theory allows you to… • Consider choice situations systematically • Tease apart underlying processes • Sensitivity • d’ (“d prime”) • Signal to noise ratio • Information characteristics • Bias • beta (criterion) • Likelihood of response • Demand characteristics