Thinking is the attempt to resolve doubt about: Thinking is one determinant of actions. Others are learning, reflexes, and emotions.

Thinking = search + inference

Search for:

Diagram of the search-inference framework

Example: Iraq war

Getting into the war


An example of a bias: Outcome bias

A fault condemned but seldom avoided is the evaluation of the intention of an act in terms of the act's outcome. An agent who acted as wisely as the foreseeable circumstances permitted is censured for the ill-effects which come to pass through chance or through malicious opposition or through unforeseeable circumstances. Men desire to be fortunate as much as they desire to be wise, but yet they fail to discriminate between fortune and wisdom or between misfortune and guilt (Arnauld, 1662/1964, p. 285)

Item used by Baron and Hershey (1988)

A 55 year old man had a heart condition. He had to stop working because of chest pain. He enjoyed his work and did not want to stop. His pain also interfered with other things, such as travel and recreation.

A type of bypass operation would relieve his pain and increase his life expectancy from age 65 to age 70. However, 8% of the people who have this operation die from the operation itself.

His physician decided to go ahead with the operation. The operation succeeded.

Evaluate the physician's decision to go ahead with the operation.

Another item

A 25-year-old man is unmarried and has a steady job. He receives a letter inviting him to visit Quiet Pond Cottages, where he has been considering buying some property. As a prize for visiting the property, he is given a choice between:

Option 1. $200.

Option 2. An 80% chance of winning $300 and a 20% chance of winning nothing.

He must mail in his decision in advance, and he will be told the outcome of Option 2 whether he chooses it or not.`

Design issues

Normative model: what subjects think vs. independence of outcome

Within-S transparent vs. within-S hidden vs. between-S

Types of models

Standard for evaluation
What is the right answer for this task? Why?
Psychological explanation of departure from normative
Heuristics, strategies, mathematical models, perceptual principles, mental models
"Bias" = systematic and non-normative
Advice or prescription: heuristics, decision analysis
Designed to increase evaluation by normative standard
"Irrational" = departure from prescriptive?

Other normative models of inference:


Normative models are standards:

Descriptive models take several approaches:

Prescriptive models are addressed to different audiences:

Basic descriptive principles

Big table

Example of Polya's heuristic methods

x4 - 13x2 + 36 = 0

Could you imagine a more accessible related problem?

Naive theories (Roncato & Rumiati, 1986)

Wertheimer on understanding

Transfer problems

Kye's method (Ginsberg, "Children's arithmetic")


Teacher: "You can't take 8 from 4, so ..."

Kye: "Oh, yes you can. 4 minus 8 is negative 4. And 40 and negative 4 give you 36."


Another example from Ginsberg

  16      16+9=25 (counting out)
 + 9 
I: So when we count we get 25 and when we do it this way we get 15. Is that okay to get two answers or do you think there should be only one?
S: (Shrugs his shoulders.)
I: Which one do you think is the best answer?
S: 25
I: Why?
S: I don't know.
I: If we had 16 cookies and 9 more, would we have 15 altogether?
S: No.
I: Why not?
S: Because if you counted them together you would get 25.
I: But is this (points to the answer of 15) right sometimes? or is it always wrong?
S: It's always right.

Perkins and Baron compared


Summary: Approaches to thinking errors

Insufficient search for alternative models


Naive theories

Failure to understand