Signal Detection Theory

Question 1

Signal Detection Theory (Goldstein)

Answer 1

Response Criterion :

• Criterion by which the Responder decides whether a signal was detected or not.

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Question 2

ROC Curve

Answer 2

Receiver operating characteristics :

• A curve which does plot the sensitivity against the specificity ( rate of false alarms / rate of hits)
• In this curve it can be determined whether a person is rather liberal or conservative in their signal detection criterion.

Question 3

Probability Distribution

Answer 3

• does represent the probability of a response - given a signal actually occurred.
• entails 2 curves

N -> the probability that a given answer will be due to noise

where the curves overlaps, it is hard to decide whether one listens to noise or a Signal.

S+N –> probability that a given answer will be due to Noise and the Signal.

Question 4

Criterion

Answer 4

Participants have their individual criterion to differentiate between noise and signal.

Pp can either be conservative, neutral or liberal.

Liberal criterion
N: most of the probability distribution to the right: good changes of “yes”: good chance of a false alarm
S+N: entire probability distribution to the right: very high chance of “yes”: good chance of a hit

Neutral criterion
N: only small proportion to the right: small probability of “yes”: low rate of false alarms
S+N: most of the distribution to the right: frequent “yes”: fairly high hit rate

Conservative criterion
N: none/ almost none of the probability distribution to the right: small probability of “yes”: low rate of false alarms
S+N: only small proportion to the right: small probability of “yes”: small amount of hits

Question 5

Beta

Answer 5

Ratio of neural activity produced by signal and noise at XC (correlated with XC): β= P(XIS)P(XIN)

Optimal beta: minimal probability of error, depends on likelihood of observing a signal.

β optimal= P(N)P(S)
β =1: signal occurs as often as it doesn’t
β >1: signal occurs more often than it doesn’t: criterion should be lowered
β<1: signal doesn’t occur more often than it does: should be increased

–> the criterion should be lowered or hightened depending on whether the costs are higher for false rejections or false alarms.

Question 6

d’ sensitivity

Answer 6

Sensitivity to detect a signal.

Question 7

Riecke Study

Answer 7

Participants were more likely to judge a discontinuous tone as continuous is they previously listened to a tone containing a clear gap (soft adaptor), rather than a tone not containing a clear gap (loud adaptor).
If the gap was clear before, ambiguity after would trip them up.