BazermanMoore

18 Chapter 2: Common Biases
BIASES EMANATING FROM THE AVAILABILITY HEURISTIC
Bias 1: Ease of Recall (based on vividness and recency)
Problem 1. Please rank order the following causes of death in the United States between
1990 and 2000, placing a 1 next to the most common cause, 2 next to the second most
common, etc.
___ Tobacco
___ Poor diet and physical inactivity
___ Motor vehicle accidents
___ Firearms (guns)
___ Illicit drug use
Now estimate the number of deaths caused by each of these five causes between 1990 and
2000.
It may surprise you to learn that, according to the Journal of the American Medical
Association (Mokdad, Marks, Stroup, & Gerberding, 2004, p. 1240), the causes of death
above are listed in the order of frequency, with tobacco consumption causing the most
deaths and illicit drug use causing the fewest. Even if you got the order right or came
close, you probably underestimated the magnitude of difference between the first two
causes and the last three causes. The first two causes, tobacco and poor diet/physical
inactivity, resulted in 435,000 and 400,000 annual deaths, respectively, while the latter
three causes resulted in far fewer deaths—43,000, 29,000, and 17,000 deaths, respectively.
Vivid deaths caused by cars, guns, and drugs tend to get a lot of press coverage.
The availability of vivid stories in the media biases our perception of the frequency of
events toward the last three causes over the first two. As a result, we may underestimate
the likelihood of death due to tobacco and poor diet, while overestimating the hazards
of cars, guns, and drugs.
Many life decisions are affected by the vividness of information. Although most
people recognize that AIDS is a devastating disease, many individuals ignore clear data
about how to avoid contracting AIDS. In the fall of 1991, however, sexual behavior in
Dallas was dramatically affected by one vivid piece of data that may or may not have
been true. In a chilling interview, a Dallas woman calling herself C.J. claimed she had
AIDS and was trying to spread the disease out of revenge against the man who had
infected her. After this vivid interview made the local news, attendance at Dallas AIDS
seminars increased dramatically, AIDS became the main topic of Dallas talk shows, and
requests for HIV tests surged citywide. Although C.J.’s possible actions were a legitimate
cause for concern, it is clear that most of the health risks related to AIDS are not
a result of one woman’s actions. There are many more important reasons to be concerned
about AIDS. However, C.J.’s vivid report had a more substantial effect on many
people’s behavior than the mountains of data available.
The availability heuristic describes the inferences we make about event commonness
based on the ease with which we can remember instances of that event. Tversky
and Kahneman (1974) cite evidence of this bias in a lab study in which individuals
were read lists of names of well-known personalities of both genders. Different