Intelligence

It has been argued that intelligence has three basic meanings: (1) it is a genetic capacity, (2) it is an observed behavior, the interaction of genes and the environment, and (3) it is what an intelligence test measures.

Intelligence has long been viewed as static and biologically determined. In 1869 Sir Francis Galton published Hereditary Genius, in which he proposed that “genius” ran in certain families, one of which was his own. At the beginning of the twentieth century, specifically 1904, Charles Spearman theorized that intelligence was the composite of several factors, a general g factor and a series of specific s factors. Spearman assumed that in any specific situation, the g factor activated a set of “specific engines” of ability. Spearman believed the general intelligence (g) factor was largely inherited, but the specific s factors were susceptible to environmental influences.

In 1935 L. L. Thurstone challenged the g theory in The Vectors of the Mind. Thurstone proposed that intelligence was a composite of special factors, each unique to a specific task. He identified seven factors or primary abilities that were independent of one another and free of any overarching general intelligence factor. The seven vectors are verbal comprehension, word fluency, number and computational abilities, spatial visualization, associative memory, perceptual speed, and reasoning ability.

In the 1940s Studies in the Development of Young Children, psychologist Nancy Bayley challenged the static view of intelligence, finding in longitudinal research with her colleagues at the University of California, Berkeley that (a) IQs are not constant—there is considerable variation in measured intelligence over time, (b) IQ variability is greatest during the first few years of life—the older the child, the greater the IQ stability, (c) intellectual ability may continue to grow through life—environmental stimulation plays an important role in whether intellectual function grows or declines, and (d) the components of intellect change with age level.

David Weschsler, developer of one of the most widely used intelligence scales in 1958, defined intelligence as the capacity for purposeful, rational, and effective action. Research over the last 20 years has further expanded our understanding of intelligence. Howard Gardner developed a theory of multiple intelligences by drawing on theories of intelligence and research on savants, prodigies, and other exceptional individuals. In Frames of Mind in 1983, Gardner postulated that there are seven human intelligences: linguistic, musical, logical-mathematical, spatial, kinesthetic, interpersonal, and intrapersonal. In the [Page 515]mid-1990s Gardner identified an eighth intelligence—naturalist (see Table 1). And in The Disciplined Mind in 1999, Gardner suggests that perhaps human beings also display a ninth intelligence—questioning life, death, and other ultimate questions.

Gardner characterized the intelligences as independent but connected or interdependent in an overall context. He also proposed that every individual has all eight intelligences but that each individual relies on or has a preference for his or her particular blend of intelligences.

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