Task 2

Question 1

d’

Answer 1

sensitivity of the subject, detectability of the signal , difficulty of the detection task
• d’ = 0: poor sensitivity/detectability = just guessing
• d’ > 0: good sensitivity/detectability
• d’ < 0 : ‘good’ sensitivity/detectability but systematic error (confusion of “yes” and “no”)

Question 2

Signal detection theory

Answer 2

• Method that measures the ability to differentiate between information patterns (stimulus/signal) and random patterns that distract from the information (noise)
• Number of factors affect how a detecting system will detect a signal & where its threshold levels will be
• Offers A look into the ‘black box’ (i.e., brain) based on simple “Yes/No” responses

Question 3

Assumptions pf SDT:

Answer 3

1) Internal noise has a specific distribution across trials (usually standard Gaussion = normal)
2) Same noise distribution of N trials and S+N trials (noise is constant)
3) Signal and noise add up linearly (do not interact)

Question 4

Concept of absolute threshold

Answer 4

• Subjects may employ different strategies
• Liberal (= indicating lower threshold)
• Conservative (= indicating a higher threshold)
• Because factors other than sensitivity to signal may influence results, signal detection experiments have been employed

Question 5

Signal and noise

Answer 5

• Experiments always involve presenting either signal plus noise (S+N) or simply noise (N) because noise will always be present
• The smaller the difference in intensity between signals and noise, the greater the error probability

Question 6

Probability distributions:

Answer 6

-Both S+N and N have a probability distribution
-Tells us the chances that a given signal is due to N or S+N
-Overlap: for some perceptual effects, the judgement will be difficult
-Shaded area must sum to one:
P (H) + P (M) = 1 and P (FA) + P (CR) = 1