Monday, August 27, 2012

confirmation bias

Confirmation bias refers to a type of selective thinking whereby one tends to notice and look for what confirms one's beliefs, and to ignore, not look for, or undervalue the relevance of what contradicts one's beliefs. For example, if you believe that during a full moon there is an increase in admissions to the emergency room where you work, you will take notice of admissions during a full moon but be inattentive to the moon when admissions occur during other nights of the month. A tendency to do this over time unjustifiably strengthens your belief in the relationship between the full moon and accidents and other lunar effects.

This tendency to give more attention and weight to data that support our beliefs than we do to contrary data is especially pernicious when our beliefs are little more than prejudices. If our beliefs are firmly established on solid evidence and valid confirmatory experiments, the tendency to give more attention and weight to data that fit with our beliefs should not lead us astray as a rule. Of course, if we become blinded to evidence truly refuting a favored hypothesis, we have crossed the line from reasonableness to closed-mindedness.

Monday, August 20, 2012


Study after study has found that the vast majority of people think they are above average, less biased, more congenial, less susceptible to improper influence, and more competent than the majority of their peers.

Ninety-four percent of university professors think they are better at their jobs than their colleagues. Seventy percent of college students think they are above average in leadership ability. Only two percent of college students think they are below average in leadership ability. Twenty-five percent of college students believe they are in the top one percent in terms of their ability to get along with others.

Eighty-five percent of medical students think it’s improper for politicians to accept gifts from lobbyists, but only forty-six percent of medical students think it’s improper for physicians to accept gifts from drug companies. A study of medical residents found that eighty-four percent thought that their colleagues were influenced by gifts from pharmaceutical companies, but only 16 percent thought that they were similarly influenced.

Monday, August 13, 2012

regressive fallacy

The regressive fallacy is an error in causal reasoning: the failure to take into account natural and inevitable fluctuations when ascribing causes to events (Gilovich 1993: 26). Golf scores and chronic back pain, for example, inevitably fluctuate. Periods of low scores or little or no pain are eventually followed by periods of higher scores or more intense pain. Ignoring natural fluctuations can easily lead to the availability bias driving one to confirm a favored causal explanation based on little more than that one thing happened after the other (the post hoc fallacy).

A professional golfer with chronic back pain or arthritis, for example, might try a copper bracelet on his wrist or magnetic insoles in his shoes when he is not playing or feeling well. He notices that his scores are improving and his pain is diminishing or gone. He concludes that the copper bracelet or the magnetic insole is the cause of his feeling and playing better. He doesn't consider that the scores and the pain are probably improving due to natural and expected fluctuations. Nor does it occur to him that he could check a record of all his golf scores to see what kind of fluctuation in scoring has occurred in the past. If he takes his average score as a base, most likely he would find that after a very low score he tended to shoot not a lower score but a higher score in the direction of his average. Likewise, he would find that after a very high score, he did not tend to shoot another higher score but rather would shoot a lower score in the direction of his average. In fact, overall it is inevitable that a golfer's scores tend toward the average.

Monday, August 6, 2012

illusion of skill

The illusion of skill refers to the belief that skill, not chance or luck, accounts for the accuracy of predictions of things that are unpredictable, such as the long-term weather forecasts one finds in farmers' almanacs and the predictions of market gurus about the long-term ups and downs of the stock market. The illusion of skill also accurately describes the apparent accuracy of remote viewers. Given all the guesses remote viewers make about what they claim to see telepathically, chance alone would account for some of those guesses being somewhat accurate. Much of the accuracy ascribed to remote viewers, however, is due to the liberal and generous interpretations given by themselves or "experts" of their vague and ambiguous descriptions of places or things. Also, subjective validation accounts for the illusion of skill of "experts" in such fields as palm reading, mediumship, astrology, and criminal profiling.