Lecture 5 - Signal detection theory

Question 1

(lecture):

Describe the 2 big problems in decision making.

Answer 1

(lecture):

See blue writing on page 1-2 G doc notes.

Question 2

(lecture):

Describe Signal detection theory.

Answer 2

(lecture):

See red writing on page 2 of G doc notes.

Question 3

(lecture):

Describe continuous, variable evidence.

Answer 3

(lecture):

See blue writing on page 4 of G doc notes.

Question 4

(lecture):

Read orange writing on page 4 of G doc notes.

Answer 4

(lecture):

Question 5

(lecture):

Describe “Performance” vs Sensitivity.

Answer 5

(lecture):

See purple writing on page 6 of G doc notes.

Question 6

(lecture):

Read red writing on page 7 of G doc notes.

Answer 6

(lecture):

Question 7

(lecture):

Signal detection theory:
(summary)
- Continuous psychological variables turned into binary decisions
- visible symptoms of illness
- feeling of familiarity of a face
- sense that a stimulus or body was moving

Performance determined by two independent processes
- chosen response criterion: how willing/unwilling you are to say ‘yes’ to something
> liberal criterion: say ‘yes’ without very strong evidence
> conservative criterion: only say ‘yes’ when you’ve got strong evidence

• relative degree of evidence elicited by stimuli belonging to Target and Distractor classes
  > people who are ill vs. people who are well
  > people you have seen before vs. people you haven’t
  > moving stimuli vs. static stimuli

Answer 7

(lecture):

Question 8

(lecture):

This is how we take evidence, make a judgement and integrate everything into a decision. The decision is different from the judgement as it is not discrete and something you cannot take back (unlike a judgement which may be more variable). This lecture will be discussing this decision process and modelling how we do it.

Things to get out of this lecture:
- Signal detection theory as a general theory of decision making, with two components
> the extent to which the evidence we’re using to base a decision on distinguishes between the outcome/thing we’re interested in and those we’re not (sensitivity/discriminability)
> how strong that evidence needs to be for us to make a decision one way or the other (decision criterion)

• The different outcomes that follow a decision, and how they may affect the decision- making process

Answer 8

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Question 9

(lecture):

See green writing on page 8 of G doc notes for homework questions.

Answer 9

(lecture):