Advanced Research Methods PSYC325 Signal Detection Theory with special thanks to Dr. Murray White

# Advanced Research Methods PSYC325 Signal Detection Theory with special thanks to Dr. Murray White

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## Advanced Research Methods PSYC325 Signal Detection Theory with special thanks to Dr. Murray White

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1. Advanced Research MethodsPSYC325Signal Detection Theorywith special thanks to Dr. Murray White Dr. Jan Lauwereyns EA619, ext. 5042 Jan.Lauwereyns@vuw.ac.nz

2. 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.

3. Response Stimulus Stimulus – Response Matrix

4. Response Stimulus Response Stimulus

5. Special die: three or naught

6. 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…

7. If the total is 6… Special die = 0 Special die = 3

8. Possible outcomes of each throw You say… The special die is…

9. > > > > > >

10. > 7 > 10

11. > 7 > 10

12. > 7 > 10 +\$120 -\$120

13. 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’

14. Special die with 3’s and O’s There is no 3 There is a 3 Total of the three dice

15. Special die with 6’s and O’s There is no 6 There is a 6 Total of the three dice

16. Left liberal

17. Right conservative

18. beta versus d’ • Effects of • signal-to-noise ratio (d’) • decision criteria (beta) • Effects of • perceptual sensitivity • response bias

19. 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

20. Lauwereyns et al. (2002, Neuron): “wishful seeing” Reward leads to general increase of neural activity = bias effect; no change in d’

21. 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