Signal Detection Theory

Brief concepts Green, D. M., & Swets, J. A. (1966). Signal Detection Theory and Psychophysics. New York: John Wiley.

Stimulus – Response Matrix Response Stimulus

Response

Special die: three or naught

If the total is 3… If the total is 14… If the total is 8… The special die has to be 0 The special die has to be 3 The special die can be either 0 or 3

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

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

> > > > > >

> 7 > 10

> 7

> 10 > 7 +$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’

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

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

Left liberal

Right conservative

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 Biederman & co. Context facilitates the perception of congruent objects De Graef, Henderson, Hollingworth There is only a response bias

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