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What Intelligence Tests Miss

In his excellent book, What Intelligence Tests Miss: The Psychology of Rational Thought, cognitive scientist Keith Stanovich argues that popular intelligence tests do not measure key rational thinking skills. Intelligence tests measure important mental abilities, but they are radically incomplete in assessing the full spectrum of important cognitive skills. Being intelligent does not necessarily mean being a good thinker.

Carol Tarvis, Ph.D., coauthor of Mistakes Were Made (But Not By Me): Why We Justify Foolish Beliefs, Bad Decisions, and Hurtful Acts, commented:

In this smart and rational book, Keith Stanovich explains the difference between intelligence and rationality. Stanovich, one of psychology’s wisest writers about intelligence, also shows that IQ tests do not measure the full scope of mental ability because they fail to assess rational thought, which is central to happiness and fulfillment. This book is essential reading for anyone who wants to know what makes us truly smart — and why smart people often behave irrationally.

Daniel Kahneman, Princeton University, Nobel Laureate in Economics commented:

In this compellingly readable book Keith Stanovich explains the bold claim that the notions of rationality and intelligence must be distinguished sharply and studied separately. His proposal would deeply change both the field of intelligence testing and the study of individual decision making — and he may well succeed.

Chapter 1 is titled “Inside George W. Bush’s Mind: Hints at What IQ Tests Miss.” The chapter opens by discussing a surprising finding, that Bush’s estimated IQ score is the same (120) as his 2004 presidential election opponent, John Kerry. Bush’s cognitive weaknesses do not impair his ability to score high on intelligence tests, but they do negatively affect his rational thinking skills. Stanovich explains that these cognitive weaknesses are the cause of “dysrationalia,” defined as “the inability to think and behave rationally despite having adequate intelligence.” Stanovich coined the term in the mid-1990s.

To be clear, Stanovich is not trying to bash intelligence tests or say they are worthless:

IQ tests measure something that is cognitively real and that does relate to real life (p. 6).

To reiterate, there is more to good thinking than intelligence (as defined by popular intelligence tests and their proxies, such as the SAT).

What is rationality? Cognitive scientists divide rationality into two broad categories, instrumental and epistemic. Instrumental rationality is defined as adopting appropriate goals, and behaving in a manner that maximizes the potential to attain those goals. Epistemic rationality is defined as holding beliefs that are commensurate with available evidence. The two types are related.

In Chapter 3 Stanovich presents a model of the mind. Evidence from cognitive psychology and neuroscience “is converging on the conclusion that the functioning of the brain can be characterized by two different types of cognition having somewhat different functions and different strengths and weaknesses” (pp. 21-22). These two different types of cognition are referred to as Type 1 and Type 2 processing. Type 1 processing is computationally inexpensive, and executes rapidly. Type 2 processing is relatively slow and computationally expensive. Many Type 1 processes can function at once in parallel, but one or very few Type 2 processes can function at once. In the book, both types of processing are explained in detail.

Stanovich expands on the previous dual-process views of the mind and introduces a tripartite model. Previous dual-process views “tended to ignore individual differences and hence to miss critical differences in Type 2 processing” (p. 33). The tripartite model include the autonomous, algorithmic and reflective mind.

To be rational you need the appropriate mindware, a term coined by cognitive scientist David Perkins. Mindware refers to information stored in memory that can be retrieved to assist in problem-solving and decision-making. This special mindware includes adequate knowledge in the areas of logic, scientific thinking, probabilistic thinking, and causal reasoning. Stanovich points out these domains of knowledge are not adequately assessed by intelligence tests.

Stanovich argues that we overvalue the term intelligence, and sometimes confuse other good thinking skills for intelligence. Intelligence and rationality are often dissociated.

The good news is rationality can be learned. It appears that rationality may be more malleable than intelligence.

I would highly recommend this book to anyone interested in cognition. The book is suitable both for a lay audience or one with more advanced knowledge.

What Intelligence Tests Miss

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Jamie Hale, M.S.

Jamie Hale, MS., is a researcher specializing in eating behavior, cognitive science (various aspects) and scientific reasoning. Jamie has written seven books and co-authored one. He is a member of the World Martial Arts Hall of Fame (recognition of my strength and conditioning work with martial artists), college instructor, learning / memory consultant and board member of Kentucky Council Against Health Fraud. Visit Jamie's site at

Scientifically Reviewed
Last updated: 17 May 2016
Last reviewed: By a member of our
scientific advisory board on 17 May 2016
Published on Psych All rights reserved.