Occam's razor – 1Occam's razor – 1

The The Occam's razorOccam's razor principle principle (of William of (of William of

Ockham)Ockham) states that the explanation of states that the explanation of

any phenomenon should make as few any phenomenon should make as few

assumptions as possible, eliminating, or assumptions as possible, eliminating, or

"shaving off", the observable "shaving off", the observable

predictions of the explanatory predictions of the explanatory

hypothesis or theory.hypothesis or theory.

(see Wikipedia)(see Wikipedia)

Occam's razor – 2Occam's razor – 2

Given two equally valid explanations for a Given two equally valid explanations for a

phenomenon, one should embrace the phenomenon, one should embrace the

less complicated formulation. less complicated formulation.

And, when multiple competing theories And, when multiple competing theories

have equal predictive powers, select those have equal predictive powers, select those

that introduce the fewest assumptions and that introduce the fewest assumptions and

the fewest hypothetical entities.the fewest hypothetical entities.

BiasBias Critical thinking does not assure that one Critical thinking does not assure that one

will reach either the truth or correct will reach either the truth or correct conclusions.conclusions.

First, one may not have all the relevant First, one may not have all the relevant information; indeed, important information information; indeed, important information may remain undiscovered, or the may remain undiscovered, or the information may not even be knowable.information may not even be knowable.

Second, one's biases may prevent effective Second, one's biases may prevent effective gathering and evaluation of the available gathering and evaluation of the available information. information.

Bias typesBias types

Decision making biasesDecision making biases

Behavioural biasesBehavioural biases

Biases in probability and beliefBiases in probability and belief

Social biasesSocial biases

Decision making + behavioural biases Decision making + behavioural biases 11

Bandwagon effectBandwagon effect - the tendency to do or believe - the tendency to do or believe

things because many others do or believe the things because many others do or believe the

same. same.

Bias blind spotBias blind spot - the tendency not to compensate - the tendency not to compensate

for one's own cognitive biases. for one's own cognitive biases.

Choice-supportive biasChoice-supportive bias - the tendency to remember - the tendency to remember

one's choices as better than they actually were. one's choices as better than they actually were.

Confirmation biasConfirmation bias - the tendency to search for or - the tendency to search for or

interpret information in a way that confirms one's interpret information in a way that confirms one's

preconceptions. preconceptions.

Decision making + behavioural biases Decision making + behavioural biases 22

Congruence biasCongruence bias - the tendency to test - the tendency to test

hypotheses exclusively through direct testing, hypotheses exclusively through direct testing,

without considering testing their without considering testing their

consequences.consequences.

Contrast effectContrast effect - the enhancement or - the enhancement or

diminishment of a weight or other diminishment of a weight or other

measurement when compared with recently measurement when compared with recently

observed contrasting object. observed contrasting object.

Disconfirmation biasDisconfirmation bias - the tendency to - the tendency to

extend critical scrutiny to information extend critical scrutiny to information

which contradicts prior beliefs, and to which contradicts prior beliefs, and to

accept uncritically information that is accept uncritically information that is

congruent with prior beliefs.congruent with prior beliefs.

Endowment effectEndowment effect - the tendency to value - the tendency to value

something more as soon as you own it. something more as soon as you own it.

Decision making + behavioural biases Decision making + behavioural biases 33

Decision making + behavioural biases Decision making + behavioural biases 44

Focusing effectFocusing effect - prediction bias occurring - prediction bias occurring

when you place too much importance on one when you place too much importance on one

aspect of an event; causes error in accurately aspect of an event; causes error in accurately

predicting the utility of a future outcome. predicting the utility of a future outcome.

Hyperbolic discountingHyperbolic discounting - the tendency to have - the tendency to have

a stronger preference for more immediate a stronger preference for more immediate

payoffs relative to later payoffs, the closer to payoffs relative to later payoffs, the closer to

the present time both payoffs are. the present time both payoffs are.

Decision making + behavioural Decision making + behavioural biases 5biases 5

Illusion of controlIllusion of control - the tendency to believe - the tendency to believe

you can control or at least influence you can control or at least influence

outcomes which you clearly cannot.outcomes which you clearly cannot.

Impact bias - the tendency to overestimate Impact bias - the tendency to overestimate

the length or the intensity of the impact of the length or the intensity of the impact of

future feeling states. future feeling states.

Information bias - the tendency to seek Information bias - the tendency to seek

information even when it cannot affect information even when it cannot affect

action. action.

Decision making + behavioural Decision making + behavioural biases 6biases 6

Loss aversion - the tendency to strongly Loss aversion - the tendency to strongly

prefer avoiding losses over acquiring gains.prefer avoiding losses over acquiring gains.

Neglect of probability - the tendency to Neglect of probability - the tendency to

completely disregard probability when completely disregard probability when

making a decision under uncertainty.making a decision under uncertainty.

Mere exposure effect - the tendency to Mere exposure effect - the tendency to

express undue liking for things merely express undue liking for things merely

because they are familiar to you.because they are familiar to you.

Decision making + behavioural biases Decision making + behavioural biases 77

Omission biasOmission bias - The tendency to judge harmful - The tendency to judge harmful

actions as worse, or less moral than equally actions as worse, or less moral than equally

harmful omissions (inactions). harmful omissions (inactions).

Outcome biasOutcome bias - the tendency to judge a - the tendency to judge a

decision by its eventual outcome instead of decision by its eventual outcome instead of

based on the quality of the decision at the based on the quality of the decision at the

time it was made. time it was made.

Planning fallacyPlanning fallacy - the tendency to - the tendency to

underestimate task-completion times. underestimate task-completion times.

Decision making + behavioural biases Decision making + behavioural biases 77

Post-purchase rationalizationPost-purchase rationalization - the tendency - the tendency

to persuade oneself through rational to persuade oneself through rational

argument that a purchase was good value. argument that a purchase was good value.

Pseudocertainty effectPseudocertainty effect - the tendency to - the tendency to

make risk-averse choices if the expected make risk-averse choices if the expected

outcome is positive, but make risk-seeking outcome is positive, but make risk-seeking

choices to avoid negative outcomes. choices to avoid negative outcomes.

Decision making + behavioural biases Decision making + behavioural biases 88

Rosy retrospection - the tendency to rate Rosy retrospection - the tendency to rate

past events more positively than you had past events more positively than you had

actually rated them when the event occurred. actually rated them when the event occurred.

Selective perceptionSelective perception - the tendency for - the tendency for

expectations to affect perception. expectations to affect perception.

Status quo biasStatus quo bias - the tendency to like things - the tendency to like things

to stay relatively the same. to stay relatively the same.

Decision making + behavioural Decision making + behavioural biases 9biases 9

von Restorff effect - the tendency for an item von Restorff effect - the tendency for an item

that "stands out like a sore thumb" to be that "stands out like a sore thumb" to be

more likely remembered than other items. more likely remembered than other items.

Zero-risk bias - preference for reducing a Zero-risk bias - preference for reducing a

small risk to zero over a greater reduction in small risk to zero over a greater reduction in

a larger risk.a larger risk.

Biases in probability and belief Biases in probability and belief - 1- 1

Ambiguity effectAmbiguity effect - the avoidance of options for - the avoidance of options for which missing information makes the probability which missing information makes the probability seem "unknown". seem "unknown".

AnchoringAnchoring - the tendency to rely too heavily, or - the tendency to rely too heavily, or "anchor", on one trait or piece of information "anchor", on one trait or piece of information when making decisions.when making decisions.

Anthropic biasAnthropic bias - the tendency for one's evidence - the tendency for one's evidence to be biased by observation selection effects.to be biased by observation selection effects.

Attentional biasAttentional bias - neglect of relevant data when - neglect of relevant data when making judgments of a correlation or making judgments of a correlation or association.association.

Biases in probability and belief Biases in probability and belief - 2- 2

Availability heuristicAvailability heuristic - a biased prediction, - a biased prediction, due to the tendency to focus on the most due to the tendency to focus on the most salient and emotionally charged outcome. salient and emotionally charged outcome.

Belief biasBelief bias - the tendency to base - the tendency to base assessments on personal beliefs. assessments on personal beliefs.

Belief overkillBelief overkill - the tendency to bring - the tendency to bring beliefs and values together so that they all beliefs and values together so that they all point to the same conclusion.point to the same conclusion.

Clustering illusionClustering illusion - the tendency to see - the tendency to see patterns where actually none exist.patterns where actually none exist.

Biases in probability and belief Biases in probability and belief - 2- 2

Conjunction fallacyConjunction fallacy - the tendency to - the tendency to assume that specific conditions are more assume that specific conditions are more probable than general ones.probable than general ones.

Gambler's fallacyGambler's fallacy - the tendency to - the tendency to assume that individual random events are assume that individual random events are influenced by previous random events - influenced by previous random events - "the coin has a memory"."the coin has a memory".

Hindsight biasHindsight bias - sometimes called the "I- - sometimes called the "I-knew-it-all-along" effect, the inclination to knew-it-all-along" effect, the inclination to see past events as being predictable. see past events as being predictable.

Biases in probability and belief Biases in probability and belief - 3- 3

Illusory correlationIllusory correlation - beliefs that inaccurately - beliefs that inaccurately

suppose a relationship between a certain type suppose a relationship between a certain type

of action and an effect.of action and an effect.

My side biasMy side bias - the tendency for people to fail to - the tendency for people to fail to

look for or to ignore evidence against what look for or to ignore evidence against what

they already favour.they already favour.

Neglect of prior base rates effectNeglect of prior base rates effect - the - the

tendency to fail to incorporate prior known tendency to fail to incorporate prior known

probabilities which are pertinent to the probabilities which are pertinent to the

decision at hand.decision at hand.

Biases in probability and belief Biases in probability and belief - 4- 4

Observer-expectancy effectObserver-expectancy effect - when a researcher - when a researcher expects a given result, and therefore expects a given result, and therefore unconsciously manipulates an experiment or unconsciously manipulates an experiment or misinterprets data in order to find it.misinterprets data in order to find it.

Overconfidence effectOverconfidence effect - the tendency to - the tendency to overestimate one's own abilities.overestimate one's own abilities.

Polarization effectPolarization effect - increase in strength of belief - increase in strength of belief on both sides of an issue after presentation of on both sides of an issue after presentation of neutral or mixed evidence, resulting from neutral or mixed evidence, resulting from biased assimilation of the evidence.biased assimilation of the evidence.