One way to organize your review of this chapter would be to think about its content in relation to each of the following four themes:
1. Thinking “fast” and “slow” Dual-processing theories propose that people have two systems to solve problems. The “fast” system, which humans share with other animals, is automatic, intuitive, and not available to consciousness, whereas the “slow” system may be unique to humans, is effortful, and is available to consciousness. To what extent do the various reasoning abilities, cognitive biases, and tasks used on IQ test tap “fast” versus “slow” thinking?
2. The concrete nature of human reasoning Mathematics, which is formal reasoning, plays a relatively small role in the everyday reasoning of most of us. Normally we reason by comparing the current problem situation with memories that seem relevant to that situation. You might keep this idea in mind, as a unifying theme, as you review the discussions of (a) reasoning by analogy; (b) biases in inductive reasoning; (c) the content bias and use of mental models in deductive reasoning; and (d) the role of mental sets, and overcoming mental sets, in solving insight problems.
3. Cultural and other environmental influences on reasoning Consistent with the idea that people reason concretely is the idea that people whose experiences are quite different from each other are likely to develop different reasoning abilities. In this chapter you read about (a) cross-cultural differences in responses to classification problems; (b) East-West differences in holistic versus analytic perception and thought; (c) evidence that scores on IQ tests vary across cultures and have been increasing over time as a result of cultural changes; and (d) evidence that a person’s IQ can increase or decrease over time, depending on the work environment.
4. Concepts of intelligence are rooted in correlational research Research on intelligence makes heavy use of correlational methods. If two tests or measures correlate positively with each other—that is, if people who tend to score high (or low) on one also tend to score high (or low) on the other—then they can to some degree be considered to be measures of the same underlying characteristic, though it may not be clear just what that characteristic is. As you review the section on intelligence testing, note how patterns of correlations have been used to support (a) the concept of general intelligence; (b) the claim that intelligence tests are valid predictors of academic and employment success; (c) the distinction between fluid and crystallized intelligence; and (d) the ideas that variations in mental speed, working memory, and central executive processes may contribute to variations in intelligence.
5. Limitation of the concept of heritability Heritability is a valuable concept because it brings clarity to the long-standing nature-nurture debate. It is important, however, to understand exactly what heritability means and the limitations of the concept. Heritability does not tell us about the relative roles of genes and environment in the development of a trait within an individual, but only about their relative roles in contributing to the variability of the trait within a population. If you understand the formula for heritability, you should be able to explain (a) why heritability for a trait might be different for one population than for another; (b) why heritability decreases when the environmental diversity of the population increases; (c) why heritability of a trait can be greater for adults than for children; and (d) why high heritability within a culture at a particular time is compatible with strong environmental effects across cultures and over historical time.