Tips For Trying To Think Less Irrationally

Professor Stuart Sutherland divides his book Irrationality: The Enemy Within into 23 chapters, each addressing a different aspect of why human beings are so prone to irrational, illogical, biased and erroneous thinking.

Having trotted through its allotted subject, each chapter ends with a few tentative suggestions of how to address the various biases and errors described in it.

This blog post is a summary of that advice. I have omitted tips which are so tied to specific examples that they’re incomprehensible out of context, and trimmed most of them down (and expanded a few).

The Wrong Impression

  1. Never base a judgement or decision on a single case, no matter how striking.
  2. In forming an impression of a person (or object) try to break your judgement down into his (or its) separate qualities without letting any strikingly good or bad qualities influence your opinion about the remainder: especially in interviews or medical diagnoses.
  3. When exposed to a train of evidence or information, suspend judgement until the end: try to give as much weight to the last piece of evidence as the first.
  4. Try to resist the temptation to seek out only information which reinforces the decision you have already taken. Try to seek out all the relevant information needed to make a decision.


  1. Think before obeying.
  2. Question whether an order is justified.


  1. Think carefully before announcing a decision or commitment in front of others. Once done, these are hard to change.
  2. Ask yourself whether you are doing or saying something merely because other are doing or saying it. If you have doubts, really reflect on them and gather evidence for them.
  3. Don’t be impressed by advice on a subject from someone just because you admire them, unless they are an expert on the matter in hand.
  4. Don’t be stampeded into acting by crowds. Stand aloof.

In-groups and out-groups

  1. Don’t get carried away by group decisions. Consciously formulate arguments against the group decision.
  2. If you’re forming a team or committee, invite people with different beliefs or skill sets.
  3. Reflect on your own prejudices and the ‘types’ of people you dislike or despise.

Organisational folly

(A list of errors in large organisations, which are difficult to cure, hence there are no tips at the end of this chapter.)

Misplaced consistency

  1. Beware of over-rating the results of a choice you’ve made (because the human tendency is to slowly come to believe all your decisions have been perfect).
  2. Try not to move by small steps to an action or attitude you would initially have disapproved of.
  3. No matter how much time, effort or money you have invested in a project, cut your losses if the future looks uncertain / risky.

Misuse of Rewards and Punishments

  1. If you want someone to value a task and perform well, do not offer material rewards. Appeal to their sense of responsibility and pride.
  2. If you are a manager, adopt as participatory and egalitarian a style as possible.
  3. If you want to stop children (and anyone else) from doing something, try to persuade rather than threatening them with punishment.

Drive and Emotion

  1. Don’t take important decisions when under stress or strong emotions.
  2. Every time you subdue an impulse, it becomes easier to do so.

Ignoring the Evidence (Pearl Harbour)

  1. Search for the evidence against your hypothesis, decision, beliefs.
  2. Try to entertain hypotheses which are antagonistic to each other.
  3. Respect beliefs and ideas which conflict with your own. They might be right.

Distorting the Evidence (Battle of Arnhem)

  1. If new evidence comes in don’t distort it to support your existing actions or views. The reverse: consider carefully whether it disproves your position.
  2. Don’t trust your memory. Countless experiments prove that people remember what they need to remember to justify their actions and bolster their self-esteem.
  3. Changing your mind in light of new evidence is a sign of strength, not weakness.

Making the Wrong Connections

  1. If you want to determine whether one event is associated with another, never attempt to keep the co-occurrence of events in your head. Maintain a written tally of the four possible outcomes in a 2 x 2 box.
  2. Remember that A is only associated with B if B occurs a higher percentage of the time in the presence of A than in its absence.
  3. Pay particular attention to negative cases.
  4. In particular, do not associate things together because you expect them to be, or because they are unusual.

Mistaking Connections in Medicine

(Focuses on doctors failure to use 2 x 2 tables in order to establish correct probabilities in diagnosis, so maybe the tip should be: Don’t try to calculate conditional probabilities in your head – write it down.)

Mistaking the Cause

  1. Suspect any explanation of an event in which the cause and the effect are similar to one another.
  2. Suspect all epidemiological findings unless they are supported by more reliable evidence.
  3. Consider whether an event could have causes other than the one you first think of.
  4. In allocating cause and effect, consider that they might happen in the opposite direction to that you first choose.
  5. Be sceptical of any causal relationship unless there is an underlying theory that explains it.
  6. In apportioning responsibility for an action, do not be influenced by the magnitude of its effect.
  7. Don’t hold someone responsible for an action without first considering what others would have done in their place.
  8. Don’t assume that other people are like you.

Misinterpreting the Evidence

  1. Do not judge solely by appearances. If someone looks more like an X than a Y, they may still be a Y if there are many more Ys than Xs.
  2. A statement containing two or more pieces of information is always less likely to be true than one containing only one piece of information.
  3. Do not believe a statement is true just because part of it is true.
  4. If you learn the probability of X given Y, to arrive at a true probability you must know the base rate of X.
  5. Don’t trust small samples.
  6. Beware of biased samples.

Inconsistent decisions and Bad Bets

  1. Always work out the expected value of a gamble before accepting it.
  2. Before accepting any form of gamble be clear what you want from it – high expected value, the remote possibility of winning a large sum with a small outlay, a probable but small gain, or just the excitement of gambling and damn the expense. If you seriously intend solely to make money, work out the expected value of a gamble before accepting it.
  3. Don’t be anchored by the first figure you hear; ignore it and reason from scratch.
  4. Many connected or conditional probabilities make an event more unlikely with every new addition. Conversely, the sum of numerous independent probabilities may add up to make something quite likely.


  1. Distrust anyone who says they can predict the present from the past.
  2. Be wary of anyone who claims to be able to predict the future.
  3. Try to control your own over-confidence e.g.
    • wherever possible, try to write out and calculate probabilities rather than using ‘intuition’
    • always think of arguments which contradict your position and work them through


  1. People are liable to ignore risks if told to i.e. it is managers’ responsibility to assess the risks for their staff.
  2. Insidious chronic dangers may kill more people than dramatic accidents i.e. coal pollution kills more people than nuclear accidents.

False Inferences

  1. Regression to the mean: remember that whenever anything extreme happens, chances are the next thing will be a lot less extreme: explains why second novels or albums or sports seasons are often disappointing following an award-winning first novel, album or season.
  2. If two pieces of evidence always agree, you only need one of them to make a prediction.
  3. Avoid the gambler’s fallacy i.e. the belief that a certain random event is less likely or more likely, given a previous event or a series of events i.e. if you toss a coin long enough heads must come up. No. Each new toss is a new event, uninfluenced by previous events.

The Failure of Intuition

  1. Suspect anyone who claims to have good intuition.
  2. If you are in a profession, consider using mathematical models of decision making instead of trusting your ‘intuition’.


  1. When the importance of a decision merits the expenditure of time, use Utility Theory.
  2. Before making an important decision decide what your overall aim is, whether it be to maximise the attainment of your goals, to save yourself from loss, to make at least some improvement to your situation etc.

Causes, cures and costs

  • keep an open mind
  • reach a conclusion only after reviewing all the possible evidence
  • it is a sign of strength to change one’s mind
  • seek out evidence which disproves your beliefs
  • do not ignore or distort evidence which disproves your beliefs
  • never make decisions in a hurry or under stress
  • where the evidence points to no obvious decision, don’t take one
  • learn basic statistics and probability
  • substitute mathematical methods (cost-benefit analysis, regression analysis, utility method) for intuition and subjective judgement


This is all very good advice, and I’d advise anyone to read Sutherland’s book. However, I can see scope for improvement or taking it further.

The structure above reflects Sutherland’s i.e. it has arranged the field in terms of the errors people make – each chapter devoted to a type of error with various types of evidence describing experiments which show how common they are.

In a sense this is an easy approach. There exist nowadays numerous lists of cognitive errors and biases.

Arguably, it would be more helpful to try and make a book or helpsheet arranged by problems and solutions, in which – instead of beginning another paragraph ‘Imagine you toss a coin a thousand times…’ in order to demonstrate another common misunderstanding of probability theory – each chapter focused on types real world of situation and how to handle them.

It would be titled something like How to think more clearly about… and then devote a chapter each to meeting new people, interviews, formal meetings and so on. There would be a standalone chapter devoted just to probability theory, since this stands out to me as being utterly different from the psychological biases – and maybe another one devoted solely to gambling since this, also, amounts to a specialised area of probability.

There would be one on financial advisers and stock brokers, giving really detailed advice on what to look for before hiring one, and whether you need one at all.

There would be one solely about medical statistics i.e. explaining how to understand the risks and benefits of medical treatment, if you ever need some.

Currently, although Sutherland’s book and the list of tips listed above are useful, it is impossible to remember all of them. A more practical approach would be to have a book (or website) of problems or situations where you could look up the situation and be reminded of the handful of simple but effective principles you should bear in mind.

Related link

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