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47 Cognitive Biases Investors May Be Able to Exploit
Posted by: Tannor Pilatzke (IP Logged)
Date: August 21, 2013 11:50AM

The list below is assembled from various sources including books, Blink, Nudge, Subliminal, Predictability Irrational, Sway, Made to Stick, The Science of Fear, The Black Swan, The Guinea Pig Diaries, Thinking Fast and Slow (a must read) and also Internet source Wikipedia. Additional insight may be found in the books listed above, and I have also attached links to resources that may be valuable for further research below.
  1. Anchoring - Humans put too much weight on the first piece of information offered (sometimes the average), commonly seen when we are estimating or making another type of judgement. (Wall Street analysts can commonly be found as the culprit.)
  2. Availability Fallacy - The easier it is for us to recall an event the higher probability of occurring we give to it. A great example is in the media, how obscure and freakish some of the stories reported are (particularly involving death) as others involving the same outcomes in generally greater quantities are tossed under the rug. (i.e. 6,000 die annually during trips to foreign countries versus 35 million citizens travel abroad safely).
  3. Bandwagon Effect (Argumentum Ad Populum) – We are overly influenced in how we behave and act as a majority or crowd; the fallacy concludes that we believe something is true because the majority believes it.
  4. Blind Spot Bias – We fail to compensate for those biases that we are aware of.
  5. Big Man Bias – A person of authority is perceived to be taller than he/she actually is.
  6. Choice-supportive Bias – Attributing positive characteristics to an option one has selected or attributing negative characteristics to an option that has been forgone. False memories may be born from interpretation of the experience or event.
  7. Conjunction Fallacy – Occurs when specific conditions are thought to be more probable than general ones. A great example from Daniel Kahneman & Amos Tversky helps to illustrate the fallacy in layman terms: “Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice and also participated in anti-nuclear demonstrations. Which is more probable?”
    a) Linda is a bank teller.
    b) Linda is a bank teller and is active in the feminist movement.
    (85% of people go for option b although a is clearly more probable.)
  8. Consistency Bias – Remembering your past opinions and behavior as resembling your present opinions and behavior, even though they don’t.
  9. Contrast Effect – An enhancement or diminished stimulus or feeling related to performance (i.e. lifting 50 pounds then lifting 25 pounds will feel like less than half of the original weight).
  10. The Decoy Effect – A change in preference between two options due to the introduction of a third option. (Generally the introduction of the third option makes one of the first two options look better than previously thought.)
  11. Distinction Bias – When two options are side by side we overestimate their differences or they appear more distinctive when viewed together verses in isolation.
  12. Endowment Effect [size=13px; ]– When we own something we overvalue it and perceive it as more valuable than it is.[/size]
  13. Extremeness Aversion – A tendency to avoid extremes, making an intermediate (middle ground) choice more likely to be chosen (i.e. I don’t want the most expensive, but I don’t want the cheapest either).
  14. Forer Effect – A tendency to believe general, vague descriptions suitable for anyone are accurate descriptions of ourselves (i.e. why we tend to believe, or at least partially believe, fortune tellers and horoscopes).
  15. Framing Effect – We make different decisions in regards to the same situation, based on how the option is presented (i.e. you will undergo a surgery that has a 95% survival rate, but object to a surgery with a 5% death rate).
  16. Fundamental Attribution Error [size=13px; ]– When explaining another person’s behavior, we assign too much weight to his or her personality and not the situation.[/size]
  17. Gamblers Fallacy [size=13px; ] [size= 13px; ]–The belief that isolated or random events can be influenced by the past (i.e. I flip a coin 10 times and it lands heads 9 times in a row, an [/size]illusion [size=13px; ] that tails is more likely to present itself).[/size]
    [/size]
  18. Halo Effect – Judgments of a person’s character can be influenced by our overall impression. If you like one aspect about someone the positive feeling “spills over.”
  19. Hindsight Bias – The belief something was more predictable prior to happening than it actually was. The bias leads to a feeling of “I knew it all along” and can more easily be expressed as “hindsight is 20/20.”
  20. Ikea Effect – We overvalue an object if it was difficult to assemble or we constructed it ourselves.
  21. Illusion of Control – Believing we can influence or control outcomes that we clearly cannot.
  22. Illusory Correlation – Perceiving a relationship between variables when there is none. “I always choose the slow check-out lane.”
  23. Just-World Hypothesis – Believing the world is fair and people get what they deserve. (Unfortunately good things happen to bad people and bad things happen to good people.)
  24. Lake Wobegon Effect – People overestimate their positive abilities and underestimate their negative ones.
  25. Law of Similarity – If two things look similar, humans believe that they are somehow related, whether they are or not.
  26. Mere Exposure Effect – An expression of liking something or someone because we are familiar with it or them.
  27. Omission Bias – The tendency to judge harmful actions worse than equally harmful actions.
  28. Out-Group Homogeneity Bias – Seeing members of our own group as being relatively more varied than members of other groups (i.e. derogatory remarks such as “They all look the same” stem from this bias).
  29. Overconfidence effect – Related to “Lake Wobegon Effect” when humans are “100% sure” or “99% certain” when in reality they are not associated with that high of a probability.
  30. Patternicity – Finding meaningful patterns in meaningless noise (the cloud animals or constellations humans erroneously see).
  31. Planning Fallacy – A human tendency to underestimate the time it takes to complete a task.
  32. Primary Effect – The weight of initial events more than subsequent events that follow: “first Impressions.”
  33. The Pygmalion Effect or Golem Effect [size=13px; ]– If a human is expected to perform better they will do so, or if expected to perform poorly they will do so: a self-fulfilling bias.[/size]
  34. Reactance – The urge to do the opposite of what we have been told to protect our “freedom of choice” predisposition.
  35. Recency Effect – The weight of recent events more than earlier past events.
  36. Reminiscence Bump – Your mind over-represents events that occur between ages 10 to 25.
  37. Romeo Bias – Men generally overestimate a woman’s sexual interest in them.
  38. Rosy Retrospection – We often rate events in retrospect more greatly than if they had just happened. (Vacations and traveling are great examples.)
  39. Self-Serving Bias – When you attribute internal factors to success but attribute external factors to failures.
  40. Source Amnesia – The inability to remember where, when or how we have previously learned a statistic or fact.
  41. Spontaneous Trait Transference – People unintentionally associate you with what you say about the qualities of others.
  42. Sunk Costs – We allow costs that cannot be recovered to influence our decisions. (I.e. you pre-purchase a baseball ticket and then hear they are calling for severe thunder storms, but you decide to go anyway so you don’t lose money. The decision outcome would be presumably different if you had “won” the tickets.)
  43. Unit Bias – The irrational urge to finish an entire unit. (a plate of food)
  44. Valence Effect [size=13px; ]– Overestimation that the chance something good will happen.[/size]
  45. Von Restorff Effect – Something that stands out like a sore thumb is more likely to be remembered than other items.
  46. Zeigarnik Effect [size=13px; ]– People remember uncompleted or interrupted tasks better than completed or uninterrupted ones.[/size]
  47. Zero-Risk Bias – We will overpay for the complete elimination of risk. (This is easily found in grocery stores with “organic produce.”)


Stocks Discussed: SPY, DJI, QQQ,
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