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

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Presentation on theme: "Rationality and Irrationality Rationality & Irrationality or Why are we* so foolish, and what can we do about it? * Present company excepted, of course."— Presentation transcript:

1 Rationality and Irrationality Rationality & Irrationality or Why are we* so foolish, and what can we do about it? * Present company excepted, of course.

2 Rationality and Irrationality 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?

3 Rationality and Irrationality 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

4 Rationality and Irrationality 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

5 Rationality and Irrationality 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]) Limbic circuit ‘Executive’ functions

6 Rationality and Irrationality 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?

7 Rationality and Irrationality 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

8 Rationality and Irrationality 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

9 Rationality and Irrationality 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

10 Rationality and Irrationality 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 George’s 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.

11 Rationality and Irrationality Cognitive Illusion 6: Probability blindness We don’t 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 to 0 to something which reduces it from to We reduce probabilities to certainties and deny that population probabilities apply to individual cases We mis-estimate co-variation

12 Rationality and Irrationality Covariation mis-estimation Has symptom X Doesn’t have symptom X Lives Dies 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?) From: Arkes, Harkness, & Biber (1980)

13 Rationality and Irrationality 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.

14 Rationality and Irrationality 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; Don’t 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.

15 Rationality and Irrationality 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

16 Rationality and Irrationality What can we do about our foolishness? III 6.) Don’t 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

17 Rationality and Irrationality What can we do about our foolishness? IV 9.) Don’t mistake soft-headedness for soft-heartedness 10.) Be courageous: Speak up for rationality! - Don’t be cowed by people who haven’t read or understood Bayes’ Theorem etc. - Insist on doing your job the right way, and don’t back down.

18 Rationality and Irrationality 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 today’s 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)?


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