Philosophy 145, Critical Thinking

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Class 1a: Introduction

Purpose of the Course

To help students improve their thinking about:

Is improvement needed?

Is improvement possible?

Students should learn to:

Requirements for course

For textbooks, readings, requirements, see syllabus.

Lecture notes will be posted on the course Web site each week.

Error Tendencies

An error tendency is a pattern of thinking that is natural for people but frequently leads to errors in judgments about what to believe or decisions about what to do.

Psychologists such as Gilovich often discuss error tendencies in terms of heuristics (rules of thumb in thinking) that lead to biases (systematic errors).

Philosophers such as Schick often discuss error tendencies in terms of fallacies.

Russo discusses decision traps such as plunging in, i.e. reaching a decision before thinking about what it involves.

Your portfolios will involve identification of error tendencies in real life situations.

Thinking Strategies

A good thinking strategy is a pattern of thinking that helps people overcome error tendencies in order to make true judgments and effective decisions.

Possible thinking strategies:

This is harder than it seems (Raiffa anecdote about important decisions).

Useful Distinctions


Cold vs. hot cognition:

Read chapter 1 of each of the 3 textbooks for general introduction.

Class 1b, Gilovich (ch. 2) on interpreting data

Good decision making depends on reliable beliefs

Determinants of false beliefs

1. Cognitive: imperfect strategies. Cold cognition.

2. Motivational: self-serving biases, emotions. Hot cognition.

What's wrong with having false beliefs?

1. Having false beliefs can be good, e.g. baseball?

2. But counterexamples:

a. superstition -> extinction of animals

b. wierd health practices

c. holocaust

3. Descriptive (how people think) vs. prescriptive (normative = how people should think).

Two kinds of errors in seeing patterns in data:

1. Seeing order when it isn't there. E.g. slot machines. Lottery numbers. Stock market up and down. Leukemia near power lines.


2. Failing to see order when it is there:

e.g. Semmelweiss: childbirth fever

Some cultures don't notice a link between sex and pregnancy. Doctors were slow to notice link between sex and AIDS.

General mechanism: find order in the world. Importance: risk assessment: how dangerous are pesticides, overhead power lines, etc.? Environmentalists versus industry.

"When you're hot you're hot"

Streaks in basketball, exams, gambling. Hockey?

Why do people believe in the hot hand?

Faulty intuitions about chance.

Clustering illusion: e.g. coin flips should alternate between heads and tails.

Other examples: births & full moon, etc.

We have a tendency to overgeneralize from small samples. We often don't understand randomness.

Representativeness heuristic.

Base causal judments on similarity, e.g. astrology, graphology, physiognomy

homeopathic medicine. Handwriting example.

Professor who is shy, likes to write poetry,

Professor of religion or psychology?

Need to consider baserate information.

Humans are good at pattern matching, not so good at picking up statistical regularities. "makes sense" We look for coherence, even when it isn't there.

Causal theories:

Causation is ubiquitous, but it can get in the way of understanding genuinely statistical phenomena

We can take a few instances and plug it into our preconceptions, e.g. racism, sexism.

Statistical inference can be hard, e.g. electromagnetic radiation. Link to melatonin? Jet lag.

Psychological problems result of abuse?

Cancer rates from light cigarettes just as high.

Regression fallacy.

Student has great first year? What to predict for second? Sophomore slump. Sports Illustrated jinx.

Scores are the result of ability + chance

Vividness effects:

We respond much more to salient examples.

E.g. where is a safe place to vacation?

1. California?

2. Israel?

Buying a car: Consumer Reports versus personal anecdotes.

Summary of Error tendencies:

Clustering illusion (Gilovich, ch. 2)

Tendency to see non-existent patterns in random events.

Representativeness (Gilovich, ch. 2)

Tendency to use assessments of similarity in statistical and causal reasoning.

Spurious causal theories (Gilovich, ch. 2)

Tendency to use unsupported causal theories in place of careful statistical and causal reasoning.

Regression fallacy (Gilovich, ch. 2)

Tendency for people's predictions to ignore that many statistical effects regress to the mean.

Vividness (Russo, ch. 4)

Tendency for information that is particularly salient or emotionally charged to be given undue influence.


Updated Jan. 7, 2003


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