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In January 2005, the president of Harvard University, Lawrence H. Summers, sparked an uproar during a presentation at an economic conference on women and minorities in the science and engineering workforce. During his talk, Summers proposed three reasons why there are so few women who have careers in math, physics, chemistry, and biology. One explanation was that it might be due to discrimination against women in these fields, and a second was that it might be a result of women’s preference for raising families rather than for competing in academia. But Summers also argued that women might be less genetically capable of performing science and mathematics—that they may have less “intrinsic aptitude” than do men.
Summers’s comments on genetics set off a flurry of responses. One of the conference participants, a biologist at the Massachusetts Institute of Technology, walked out on the talk, and other participants said that they were deeply offended. Summers replied that he was only putting forward hypotheses based on the scholarly work assembled for the conference, and that research has shown that genetics have been found to be very important in many domains, compared with environmental factors. As an example, he mentioned the psychological disorder of autism, which was once believed to be a result of parenting but is now known to be primarily genetic in origin.
The controversy did not stop with the conference. Many Harvard faculty members were appalled that a prominent person could even consider the possibility that mathematical skills were determined by genetics, and the controversy and protests that followed the speech led to first ever faculty vote for a motion expressing a “lack of confidence” in a Harvard president. Summers resigned his position, in large part as a result of the controversy, in 2006 (Goldin, Goldin, & Foulkes, 2005).Goldin, G., Goldin, R., & Foulkes, A. (2005, February 21). How Summers offended: Harvard president’s comments underscored the gender bias we’ve experienced. The Washington Post, p. A27. Retrieved from http://www.washingtonpost.com/wp-dyn/articles/A40693-2005Feb20.html
The characteristic that is most defining of human beings as a species is that our large cerebral cortexes make us very, very smart. In this chapter we consider how psychologists conceptualize and measure human intelligenceThe ability to think, to learn from experience, to solve problems, and to adapt to new situations.—the ability to think, to learn from experience, to solve problems, and to adapt to new situations. We’ll consider whether intelligence involves a single ability or many different abilities, how we measure intelligence, what intelligence predicts, and how cultures and societies think about it. We’ll also consider intelligence in terms of nature versus nurture and in terms of similarities versus differences among people.
Intelligence is important because it has an impact on many human behaviors. Intelligence is more strongly related than any other individual difference variable to successful educational, occupational, economic, and social outcomes. Scores on intelligence tests predict academic and military performance, as well as success in a wide variety of jobs (Ones, Viswesvaran, & Dilchert, 2005; Schmidt & Hunter, 1998).Ones, D. S., Viswesvaran, C., & Dilchert, S. (2005). Cognitive ability in selection decisions. In O. Wilhelm & R. W. Engle (Eds.), Handbook of understanding and measuring intelligence (pp. 431–468). Thousand Oaks, CA: Sage; Schmidt, F., & Hunter, J. (1998). The validity and utility of selection methods in personnel psychology: Practical and theoretical implications of 85 years of research findings. Psychological Bulletin, 124(2), 262–274. Intelligence is also negatively correlated with criminal behaviors—the average intelligence quotient (IQ) of delinquent adolescents is about 7 points lower than that of other adolescents (Wilson & Herrnstein, 1985)Wilson, J. Q., & Herrnstein, R. J. (1985). Crime and human nature. New York, NY: Simon & Schuster.—and positively correlated with health-related outcomes, including longevity (Gottfredson, 2004; Gottfredson & Deary, 2004).Gottfredson, L. S. (2004). Life, death, and intelligence. Journal of Cognitive Education and Psychology, 4(1), 23–46; Gottfredson, L. S., & Deary, I. J. (2004). Intelligence predicts health and longevity, but why? Current Directions in Psychological Science, 13(1), 1–4. At least some of this latter relationship may be due to the fact that people who are more intelligent are better able to predict and avoid accidents and to understand and follow instructions from doctors or on drug labels. Simonton (2006)Simonton, D. K. (2006). Presidential IQ, openness, intellectual brilliance, and leadership: Estimates and correlations for 42 U.S. chief executives. Political Psychology, 27(4), 511–526. also found that among U.S. presidents, the ability to effectively lead was well predicted by ratings of the president’s intelligence.
The advantages of having a higher IQ increase as life settings become more complex. The correlation between IQ and job performance is higher in more mentally demanding occupations, such as physician or lawyer, than in less mentally demanding occupations, like clerk or newspaper delivery person (Salgado et al., 2003).Salgado, J. F., Anderson, N., Moscoso, S., Bertua, C., de Fruyt, F., & Rolland, J. P. (2003). A meta-analytic study of general mental ability validity for different occupations in the European Community. Journal of Applied Psychology, 88(6), 1068–1081. Although some specific personality traits, talents, and physical abilities are important for success in some jobs, intelligence predicts performance across all types of jobs.
Our vast intelligence also allows us to have languageA system of communication that uses symbols in a regular way to create meaning., a system of communication that uses symbols in a regular way to create meaning. Language gives us the ability communicate our intelligence to others by talking, reading, and writing. As the psychologist Steven Pinker put it, language is the “the jewel in the crown of cognition” (Pinker, 1994).Pinker, S. (1994). The language instinct (1st ed.). New York, NY: William Morrow. Although other species have at least some ability to communicate, none of them have language. In the last section of this chapter we will consider the structure and development of language, as well as its vital importance to human beings.