A Reason for Reason

For all its stellar achievements, human reason seems particularly ill suited to, well, reasoning. Study after study demonstrates reason’s deficiencies, such as the oft-noted confirmation bias (the tendency to recall, select, or interpret evidence in a way that supports one’s preexisting beliefs) and people’s poor performance on straightforward logic puzzles. Why is reason so defective?

To the contrary, reason isn’t defective in the least, argue cognitive scientists Hugo Mercier of the University of Pennsylvania and Dan Sperber of the Jean Nicod Institute in Paris. The problem is that we’ve misunderstood why reason exists and measured its strengths and weaknesses against the wrong standards.

Mercier and Sperber argue that reason did not evolve to allow individuals to think through problems and make brilliant decisions on their own. Rather, it serves a fundamentally social purpose: It promotes argument. Research shows that people solve problems more effectively when they debate them in groups—and the interchange also allows people to hone essential social skills. Supposed defects such as the confirmation bias are well fitted to this purpose because they enable people to efficiently marshal the evidence they need in arguing with others.

Most people make a lot of mistakes when reasoning solo, but in group settings they tend to be quite skilled at making arguments and evaluating those of others. One study found that participants got only about 10 percent of the answers in a tough logic test correct on their own. When they worked in a group, the scores soared to 80 percent. In the absence of a challenge from others, people tend to reach for the most readily available (and often wrong) conclusion. But in groups, better arguments will win out over time.

That the human mind works best when prodded by others should come as no surprise. Over the centuries, groups and pairs of people working together have produced some of the greatest scientific achievements and philosophical dialogues. Even geniuses are quick to say they stand on the shoulders of giants. Social animals that humans are, it takes partners, colleagues, and friends to make the most of the mind.

THE SOURCE: “Why Do Humans Reason? Arguments for an Argumentative Theory” by Hugo Mercier and Dan Sperber, in Behavioral and Brain Sciences, April 2011.

Photo courtesy of ZEISS Microscopy