Rationality versus Intelligence 
.
Keith E Stanovich* | Reflection Cafe | April 15, 2009 

http://www.reflectioncafe.net/2009/04/rationality-versus-intelligence.html


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.

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