Rationality

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Rationality IrrationalityorWhy are we so
foolish,and what can we do about it?
Present company excepted, of course.
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Rationality Irrationality

• Why are we so foolish?
• The rise and fall of rationality on cognitive
  science
• An introduction to inevitable illusions
• What can we do it about our foolishness?

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The rise and fall of human rationality

• (Some proponents of) Cognitive science had high
  hopes of being a science of ideal rationality
  when it emerged
• The cleave between competence (computation) and
  performance (biology)
• This goal was stymied by evidence of
• Lack of general problem-solving methods
• Compartmentalization of knowledge
• Context effects
• A growth industry in the study of human
  foolishness Cognitive illusions

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The rise and fall of rationality on cognitive
science

• Why should this be so?

If no organic being excepting man had
possessed any mental power, or if his powers had
been of a wholly different nature from those of
the lower animals, then we should never have been
able to convince ourselves that our high
faculties had been gradually developed. But it
can be shewn that there is no fundamental
difference of this kind. We must also admit that
there is a much wider interval in mental power
between one of the lowest fishes, as a lamprey or
lancelet, and one of the higher apes, than
between an ape and man yet this interval is
filled up by numberless gradations. Charles
Darwin/ The Descent Of Man
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• The brain is constructed to find reward in
  apparent solutions (coherence) which are not the
  same as solutions (cf. Damasio, Cytowic, Bernard
  not to mention Wittgenstein Peirce)

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Cognitive Illusion 1 Over-confidence

• We are not good at judging our own confidence
  levels
• We tend to systematically err on the high side,
  and to resist attempts at correction
• The error increases as we become more certain
• We institutionalize this error by demanding
  certainty from our experts and instilling
  certainty in them
• Question Are there any good reasons to make this
  demand?

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Cognitive Illusion 2 Magical thinking

• We put great confidence in signs that derive from
  folk beliefs illusory correlations
• We will see some worrisome evidence of this in a
  later reading in this class
• Moreover, we look for evidence to support and
  sustain an priori beliefs in correlations
• we are easily taught to do so, even in the
  absence of evidence or the presence of
  counter-evidence
• Cancer cell recognition Watzlawick

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Cognitive Illusion 3 20/20 Hindsight

• The fact that something actually has happened is
  taken to mean that
• it had a high probability of happening
• that we would have known this beforehand

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Cognitive Illusion 4 Anchoring

• We use initial reference points to anchor future
  estimates
• We do so even when those initial reference points
  are (known to be) random

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Cognitive Illusion 5 Taking the easy way out
(Availability)

• We will use an easier representation rather than
  a more complex one
• The easier it is to bring an event to mind, the
  more likely we are to judge it as frequent (Uncle
  Georges Pancakes fallacy)
• This leads to under-estimation of what is
  frequent (suicide) and over-estimation of what is
  not (murder), and thereby mis-estimations of
  coincidence
• Homework Pick a random number (under 100 is
  best) and be ready for coincidences in everyday
  life about it. Report back to us.

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Cognitive Illusion 6 Probability blindness

• We dont equate equal probabilities (though fate
  does), especially at the extremes of the
  probability range
• We prefer an increase from 0.94 to 0.99 from one
  to 0.38 to 0.42, or something which reduces risk
  from 0.001 to 0 to something which reduces it
  from 0.002 to 0.001
• We reduce probabilities to certainties and deny
  that population probabilities apply to individual
  cases
• We mis-estimate co-variation

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Covariation mis-estimation
From Arkes, Harkness, Biber (1980)
Question How strong is the relation between
symptom X and death? (How worried should you be,
on a scale of 1-100, if you have symptom X?)
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Cognitive Illusion 7 Story-telling

• We over-estimate the probability of coherent
  fictions with many parts (conjunction illusion)
• Note that chains of events MUST be less probable
  than their weakest link (assuming we have no
  absolute certainty, which we never do).
• Both research and real life tell us that people
  find arguments more compelling when they support
  what they already believe anyway.

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What can we do about our foolishness?

• 1.) Distrust certainty Cultivate scepticism
• Doubt is an uncomfortable condition, but
  certainty is a ridiculous one. - Voltaire
• 2.) Keep score Dont rely on your memory.
• - Keep clinical records, compile databases
  consult them before you act.
• 3.) Do the math.
• - Use Bayes Theorem run statistical tests
  look at distribution shapes etc.

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What can we do about our foolishness? II

• 4.) Consider plausible alternatives
• - Research shows that this reduces hind-sight
  bias in some cases
• 5.) Watch out for the buddy-buddy syndrome
• The cognitive degradation and feckless
  vocalization characteristic of committees are too
  well-known to require comment. - Paul Meehl

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What can we do about our foolishness? III

• 6.) Dont weight all evidence equally ignore
  irrelevancies
• - Evidence must be differentially relevant
  (distinguish between actual possibilities) to be
  considered
• - Barnum statements true of practically
  everyone.
• 7.) Distinguish between inclusion and exclusion
  criteria
• - Failure to have an accessory symptom of X is
  not evidence against a diagnosis of X
• 8.) Remember reliability bounds
• - An insignificant difference on a test result
  is insignificant

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What can we do about our foolishness? IV

• 9.) Dont mistake soft-headedness for
  soft-heartedness
• 10.) Be courageous Speak up for rationality!
• - Dont be cowed by people who havent read or
  understood Bayes Theorem etc.
• - Insist on doing your job the right way, and
  dont back down.

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• Questions etc.
• Coincidence example from Piatelli-Palmarini How
  many people need we have in a room to have a 50
  chance that two have the same birthday?
• Is rationality always best?
• What is the role of authoritarianism in affecting
  perceptual and moral judgments?
• What is the effect of these inevitable illusions
  in todays world of mass media? (Why might the
  WWW both hinder and help rational analysis of
  probabilities?)
• How can we harness these illusions to foster
  individual well being and social harmony (without
  also fostering harmful delusion)?