Judgements and probabilities

• Anchoringtype: effect · evidence: strong

  A number you see before an estimate pulls your estimate towards it, even when you know it is random.

• Availability heuristictype: effect · evidence: supported

  We judge how often something happens by how easily examples come to mind.

• Cognitive dissonancetype: effect · evidence: contested

  When you do something that contradicts what you believe, you feel a discomfort that you reduce by changing your attitude.

• Confirmation biastype: effect · evidence: supported

  People tend to seek, choose and interpret evidence in favour of what they already believe.

• Conjunction fallacytype: effect · evidence: supported

  A more detailed story seems more probable than part of it, although every added detail makes it less probable.

• Consider the oppositetype: technique · evidence: supported

  Before drawing a conclusion or judging a piece of evidence, you ask yourself what you would think if things were the other way round.

• Dunning-Kruger effecttype: effect · evidence: supported

  People with the weakest scores on a test overestimate their performance the most.

• Framing effecttype: effect · evidence: strong

  The same choice, described in terms of gains or of losses, gets different answers.

• Gambler's fallacytype: effect · evidence: supported

  After a run of identical outcomes in a game of chance, we expect the opposite outcome to be "due", although the odds haven't changed.

• Halo effecttype: effect · evidence: strong

  The halo effect means that a positive trait that stands out, especially good looks, makes us assume a person has other qualities too.

• Hindsight biastype: effect · evidence: supported

  Once we learn how something turned out, it seems to have been predictable and we feel "I knew it all along".

• Hot hand fallacytype: effect · evidence: contested

  For more than 30 years, believing in an athlete's streaks of success was considered an illusion.

• Illusion of controltype: effect · evidence: contested

  We behave as if we could influence things that depend only on chance.

• Outcome biastype: effect · evidence: strong

  We judge a decision by how it turned out, not by how well it was thought through with what was known at the time.

• Planning fallacytype: effect · evidence: supported

  People usually underestimate how long their own projects will take, even when they know that similar projects ran late.

• Primingtype: effect · evidence: contested

  A word you see now makes you recognise related words faster.

• Pygmalion effecttype: effect · evidence: supported

  The Pygmalion effect is the idea that pupils from whom teachers expect more end up actually doing better.

• Regression to the meantype: mental model · evidence: strong

  An extreme result is usually followed by one closer to the average, even if you do nothing.