NCPA - National Center for Policy Analysis

Experience Influences Behavior in Uncertain Situations, Say Researchers

January 21, 2004

Government agencies and private companies are using an age-old theory on how individuals deal with uncertainty in order to prevent terrorism, test new medical devices and create spam filters. The method -- called Bayesian analysis -- was developed by 18th century British mathematician Thomas Bayes and suggests that the more uncertain a situation, the more an individual will rely on previous experience instead of current observation.

A study published in the journal Nature involved an experiment where participants were asked to guide a cursor from one target to the other just by moving their hand on a tabletop, with their view of their hand blocked by a screen. The cursor was always slightly to the right of their hand, and the cursor would appear either as a distinct point or a cloud. The results:

  • When the participants were able to see the cursor distinctly, they relied on it and not previous experience; however, when the cursor appeared as a more ambiguous cloud, they relied more on the 1,000 practice runs they had completed before the experiment.
  • Similarly, tennis players use previous experience to randomly mix forehand and backhand serves to gain an advantage over their opponent, according to an analysis of videotaped professional matches by University of Arizona economists.
  • However, in laboratory tests, participants tend to ignore experience -- for example, if they write down a list of outcomes from flipping a coin, they will underestimate streaks of heads or tails, knowing that the probability of heads or tails is 50-50.

Considered controversial just 10 years ago, Bayes analysis has become increasingly popular. But some researchers are skeptical, noting that while people do estimate probabilities, they do not know that it reflects the Bayes approach.

Source: David Leonhardt, "Subconsciously, Athletes May Play Like Statisticians," New York Times, January 20, 2004.

For Nature abstract


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