Intelligence, Concepts of

Intelligence, Concepts of. In 1923, the American psychologist Edwin G. Boring (1886–1968), faced with the problem of defining intelligence, famously explained that intelligence is what intelligence tests test. This seemingly circular characterization was not an off‐the‐cuff remark, but a serious attempt to deal with one of the more vexing issues confronting early twentieth‐century psychologists. From the development of the modern intelligence test by the French psychologist Alfred Binet in 1905, the practice of measuring intelligence had grown rapidly, especially in the Anglo‐American world. However, little consensus had emerged concerning the actual capability that the tests sought to measure. Some argued that intelligence referred to an individual's potential for learning or adapting to new situations, others that it denoted ability to solve problems or generate abstract ideas. And all questioned whether it was one thing or many, produced by heredity or environment, and shared with animals or uniquely human.

Interest in some mental attribute characterizing overall ability to think or reason can be traced, in the West at least, to Aristotle's definition of human beings as creatures who reason. Intelligence became a sustained topic of scientific inquiry during the late eighteenth century, when various European naturalists began to compare human beings systematically with other animals as part of their grand taxonomic projects. Such comparisons often focused on differences in intelligence and were linked by many to the notion of a “great chain of being” stretching from the simplest organisms through human beings and up to God. During the late eighteenth and early nineteenth centuries, various physical features were used to rank intelligence, with cranial capacity and brain weight predominating, especially through the labors of the American Samuel G. Morton (1799–1851). By measures such as these, a number of nineteenth‐century scientists—including the so‐called American school of anthropology, led by Morton—sought to demonstrate the inferiority of Africans by suggesting that their intelligence was closest of all human groups to that of the apes. By the century's end, however, this research program had largely been abandoned, as variations within groups proved to be much more significant than differences among them.

Apart from comparisons of races or groups, and medical assessments of profound mental deficiency, intelligence as a personal and differential characteristic elicited little concern until the later nineteenth century. Before then, American mental philosophers spoke of the intellect largely in terms of the universal attributes of human reason and conceived of the mind as possessing a wide variety of faculties or powers, a certain subset of which could be grouped under the general term “intelligence.” The advent of evolutionism, however, heightened the importance of an organism's overall mental power, as it was considered a central factor influencing progressive adaptation to the environment. At the same time, the expansion of primary education rendered differences in individual intellect more visible, and the development of the new so‐called “scientific” psychology in the late nineteenth century placed a premium on analyzing the mind in terms of quantitative methods and laboratory techniques.

The first successful psychological technique for quantifying differences in individual mental ability came early in the twentieth century. Asked in 1904 to participate in a French commission on children falling behind in the classroom, Binet and his colleague Théodore Simon created a scale of tests to identify those lagging in intellectual development. Focused on the higher mental processes and implicitly viewing intelligence itself as singular and quantifiable, the 1905 Binet‐Simon Intelligence Scale was constructed as a sequence of age‐related tasks that quantified the test‐taker's intellectual level vis‐à‐vis his or her chronological peers. Using the Binet‐Simon scale as a model, the American psychologists Henry H. Goddard and Lewis M. Terman began in the 1910s to refine the test further and link it more closely to arguments for the biological and inheritable nature of intelligence. Terman's 1916 Stanford‐Binet test, which rapidly became the dominant instrument for assessing mental ability, reported scores in terms of a chronologically invariant measure, the intelligence quotient (IQ), a ratio of mental age to chronological age developed by the German psychologist Wilhelm Stern. Frequently revised, the Stanford‐Binet test remained a leading instrument for the individual measurement of intelligence at the end of the twentieth century, although after the 1930s it was somewhat eclipsed by two scales created by David Wechsler, the Wechsler Intelligence Scale for Children (WISC) and the Wechsler Adult Intelligence Scale (WAIS).

The outbreak of World War I gave American psychologists the opportunity to promote their services and products to a broader public. Using assembly‐line‐like methods, which included the multiple‐choice question and group testing, psychologists administered mental tests to approximately 1.75 million army recruits and cited this experience in the postwar period to convince schools and industry that intelligence testing offered an efficient means of assessing students and staff. Although critics such as Walter Lippmann and William C. Bagley challenged the tests as flawed and inimical to democracy, and many business leaders shifted to measures of personality, by the end of the 1920s the concepts of “intelligence” and “intelligence assessment” were well entrenched. New instruments continued to be developed, and by the 1940s one test, the Scholastic Aptitude Test (S.A.T.), had become a gatekeeper for admission to many colleges and universities. In addition, organizations such as the Educational Testing Service (ETS) of Princeton, New Jersey, which administers the S.A.T., flourished. Founded in 1947 under the leadership of Henry Chauncey, ETS quickly became the nation's leading testing agency. In 1998, with 2,300 employees and revenues of nearly $500 million, the nonprofit ETS administered the S.A.T. and other tests to some nine million persons, signifying the continued power of the concept of intelligence.

Discussions of intelligence have historically focused on two main issues. First, is intelligence one thing or many? Beginning in 1904, the British psychologist Charles Spearman used factor analysis to argue that intelligence consists of a single mental trait he called “general intelligence” (g). Edward L. Thorndike of Columbia University, by contrast, contended that intelligence is thoroughly heterogeneous, while L.L. Thurstone of the University of Chicago argued that intelligence consists of a small number of relatively independent abilities. Later, Philip E. Vernon offered a hierarchical conception of intelligence in an attempt to achieve consensus on this issue. Nonetheless, alternative theories have abounded: in the 1960s and beyond, Joy P. Guilford argued that intelligence is composed of 150 independent factors; Howard Gardner discerned seven discrete types of intelligence; and Robert J. Sternberg contended that intelligence is triarchically organized. All the while, Spearman's (g) has continued to attract many proponents.

The second continuing issue focuses on the problem of nature versus nurture. The nineteenth‐century interest in craniometry and the ranking of species and races had assumed that intelligence was both biological and inheritable. In the early twentieth century, advocates of eugenics fortified this conviction and enlisted it to justify a variety of social programs, from ability‐tracking in high schools to sterilization of “the unfit.” Studies by the anthropologist Franz Boas in the 1910s, however, suggested that the environment plays a significant role in shaping intelligence, a position strengthened by subsequent work in the 1930s and 1940s, especially at the Iowa Child Welfare Research Station. In the post–World War II era, both heredity and environment have received much attention. Identical‐twin research was interpreted by some psychologists as indicating a close connection between intelligence and heredity. At the same time, data on the worldwide increase in IQ scores (the Flynn effect) and the demonstrated influence of nutrition and home conditions on intelligence suggested the equally strong role of environmental factors. While some interpreted the positive correlation of IQ scores with socioeconomic status as evidence of the meritocratic nature of Western societies, others argued that it underscored the culture‐bound character of all intelligence‐measurement instruments, especially when applied to the issue of IQ and race. Whether critical or supportive of intelligence testing, however, few have challenged the notion that intelligence itself is a characteristic of relevance to negotiating the contemporary world.
See also Education: The Public School Movement; Evolution, Theory of; Race, Concept of; Racism.

Bibliography

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Raymond E. Fancher , The Intelligence Men: Makers of the IQ Controversy, 1985.
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Russell Jacoby and Naomi Glauberman, eds., The Bell Curve: History, Documents, Opinions, 1995.
Kurt Danziger , Naming the Mind: How Psychology Found Its Language, 1997.
Leila Zenderland , Measuring Minds: Henry Herbert Goddard and the Origins of American Intelligence Testing, 1998.

John Carson