By Keith E. Stanovich
Project Syndicate

TORONTO ― In 2002, the cognitive scientist Daniel Kahneman of Princeton University won the Nobel Prize in Economics for work done with his longtime collaborator Amos Tversky (who died in 1996).

Their work had to do with judgment and decision-making ― what makes our thoughts and actions rational or irrational. They explored how people make choices and assess probabilities, and uncovered basic errors that are typical in decision-making.

The thinking errors they uncovered are not trivial mistakes in a parlor game. To be rational means to adopt appropriate goals, take the appropriate action given one's goals and beliefs, and hold beliefs that are commensurate with available evidence. It means achieving one's life goals using the best means possible.

To violate the thinking rules examined by Kahneman and Tversky thus has the practical consequence that we are less satisfied with our lives than we might be.

Research conducted in my own laboratory has indicated that there are systematic individual differences in the judgment and decision-making skills that Kahneman and Tversky studied.

Ironically, the Nobel Prize was awarded for studies of cognitive characteristics that are entirely missing from the most well-known mental assessment device in the behavioral sciences: intelligence tests.

Scientists and laypeople alike tend to agree that ``good thinking" encompasses sound judgment and decision-making ― the type of thinking that helps us achieve our goals. Yet assessments of such good (rational) thinking are nowhere to be found on IQ tests.

Intelligence tests measure important things, but they do not assess the extent of rational thought. This might not be such a grave omission if intelligence were a strong predictor of rational thinking.

But my research group found just the opposite: it is a mild predictor at best, and some rational thinking skills are totally dissociated from intelligence.

To an important degree, intelligence tests determine the academic and professional careers of millions of people in many countries.

Children are given intelligence tests to determine eligibility for admission to school programs for the gifted. Corporations and the military depend on assessment and sorting devices that are little more than disguised intelligence tests.

Perhaps some of this attention to intelligence is necessary, but what is not warranted is the tendency to ignore cognitive capacities that are at least equally important: the capacities that sustain rational thought and action.

Critics of intelligence tests have long pointed out that the tests ignore important parts of mental life, mainly non-cognitive domains such as socio-emotional abilities, empathy, and interpersonal skills.

But intelligence tests are also radically incomplete as measures of cognitive functioning, which is evident from the simple fact that many people display a systematic inability to think or behave rationally despite having a more than adequate IQ.

For a variety of reasons, we have come to overvalue the kinds of thinking skills that intelligence tests measure and undervalue other important cognitive skills, such as the ability to think rationally.

Psychologists have studied the major classes of thinking errors that make people less than rational.

They have studied people's tendencies to show incoherent probability assessments; to be overconfident in knowledge judgments; to ignore the alternative hypothesis; to evaluate evidence with a ``my side" bias; to show inconsistent preferences because of framing effects; to over-weigh short-term rewards at the expense of long-term well-being; to allow decisions to be affected by irrelevant context; and many others.

All of these categories of failure of rational judgment and decision-making are very imperfectly correlated with intelligence ― meaning that IQ tests tend not to capture individual differences in rational thought.

Intelligence tests measure mental skills that have been studied for a long time, whereas psychologists have only recently had the tools to measure the tendencies toward rational and irrational thinking.

Nevertheless, recent progress in the cognitive science of rational thought suggests that nothing ― save for money ― would stop us from constructing an ``RQ" test.

Such a test might prove highly useful. Suboptimal investment decisions have, for example, been linked to overconfidence in knowledge judgments, the tendency to over-explain chance events, and the tendency to substitute affective valence for thought.

Errors in medical and legal decision-making have also been linked to specific irrational thinking tendencies that psychologists have studied.

There are strategies and environmental fixes for the thinking errors that occur in all of these domains. But it is important to realize that these thinking errors are more related to rationality than intelligence. They would be reduced if schools, businesses, and government focused on the parts of cognition that intelligence tests miss.

Instead, these institutions still devote far more attention and resources to intelligence than to teaching people how to think in order to reach their goals. It is as if intelligence has become totemic in our culture.

But what we should really be pursuing is development of the reasoning strategies that could substantially increase human well-being.

Keith E. Stanovich is professor of human development and applied psychology at the University of Toronto and the author of ``What Intelligence Tests Miss: The Psychology of Rational Thought." For more stories, visit Project Syndicate (www.project-syndicate.org).