I Think, Therefore I Err

Gerd Gigerenzer I Think, Therefore I Err They all laughed at Wilbur and his brother, When they said that man couldfly. They told Marconi wireless was aphony; It’s the same old cry. — IRA GERSHWIN WHY DO WE MAKE ERRORS? ARE THEY BLUNDERS CAUSED BY THE lim itations of our cognitive system? Or are errors indispensable parts of eveiy intelligent system? From the first perspective, all errors are at best unnecessary and at worst harmful. Consider an error commonly made by children. When asked to find the sum of 1/2 and 1/3, the answer is often 2/5. This is called the freshman error of adding numerators and adding denominators (Silver, 1986). But blunders are not limited to chil­ dren. After the invention of the telephone, a group of British experts concluded that this invention had no practical value, at least in their country: “The telephone may be appropriate for our American cousins, but not here, because we have an adequate supply of messenger boys” (Sherden, 1998:175). In 1961, President John F. Kennedy is reported to have asked himself “How could I have been so stupid?” after realizing how badly he had miscalculated when he approved the Bay ofPigs inva­ sion planned by the CIA (Janis and Mann, 1977: xv). Blunders like these seem to be unnecessary as well as embarrassing, and every intelligent system would work better without them. In this view, to err is not to think. social research Vol 72 : No 1 : Spring 2005 195 From the second perspective, there are errors that need to be made—that is, errors that are indispensable and functional. I call these “good”errors. Children are known for good errors. Consider a 3-year-old who uses the phrase “I gived” instead of “I gave.” A child cannot know in advance which verbs are irregular; because irregular verbs are rare, the child’s best bet is to assume the regular form until proved wrong. The error is “good”—that is, useful—because if the 3-year-old did not try out new forms and occasionally make errors, but instead played it safe and used only those words it had already heard, she would learn a language at a veiy slow rate. The characteristic of a good error is that a person is better off making the error than not making it—for reaching a goal more quickly, or attaining it at all. In this view, every intelligent system has to make errors. Making no errors would destroy the intel­ ligence of the system. There is a close parallel to Darwinian theory, where random variability and mutation—copying errors—are essential for evolution by natural selection. Not making these errors would elim­ inate evolution. Trial-and-error learning, at the ontogenetic or evolu­ tionary level, is one source of good errors in an uncertain world. In this article, I deal with the study of human errors in experi­ mental psychology. The problem that researchers try to resolve is this: How can one infer the laws of cognition—of perception, memory, and thought? One answer is to study the systematic errors people make. At first glance, this program looks like a straightforward extension of Francis Bacon’s plan for studying nature’s errors, or of Freud’s strategy to analyze repressed memories, slips of tongue, and abnormal neurotic behavior. The idea is to catch nature when it does not pay attention— creating strange facts such as blood rain in Bavaria and an Irish girl with several horns growing on her body (Daston and Park, 1998). However, there is an important difference. We can easily see what is wrong with a goat with two heads or a man with obsessive-compulsive hand wash­ ing, and understand that it is not to the benefit of the animal or the human. Cognitive errors, however, are not as clear, as we will soon see. Here, one has to define rather than simply observe what an error of judgment is. In this article, I argue: 196 social research F ig. 1. P e rcep tu al illusion o f “ p o p -o u t” d ots. If you turn th e p ag e...