The Big Picture: Chapter Overview

Defining intelligence is the source of significant controversy in psychology. In general terms, intelligence is the ability to solve problems and to adapt and learn from experience. Research in intelligence has focused primarily on the individual differences on this psychological capacity and in the ways in which intelligence may be measured. Early psychologists, such as Sir Francis Galton, defined intelligence in terms of simple sensory, perceptual, and motor responses, as opposed to higher mental processes such as thinking and problem solving. Galton's main contribution was that he raised questions about individual differences in intelligence and how it should be assessed. One of the first significant efforts to measure intelligence was the work of Alfred Binet and his student Theofile Simon, who developed the concept of mental age to measure the individual's level of mental development relative to others. Using Binet's concepts and calculations, William Stern developed the intelligence quotient (IQ). The IQ is a calculation that determines the intelligence of a person by comparing the mental age with the chronological age. If the mental age is the same as the chronological age, the person is assessed at an average level of intelligence. If the mental age is more than the chronological age, the person is said to have an intelligence above average, and if the mental age is less than the chronological age, the person is believed to be below average in intelligence. Binet believed that intelligence was determined by the ability of a person to engage in complex cognitive processes. The current version of the original IQ test is called the Stanford-Binet and it can be administered as early as age 2 and through adulthood. It has been revised to assess abilities in four areas: verbal reasoning, quantitative reasoning, abstract/visual reasoning, and short-term memory. Extensive testing with the Stanford-Binet test has shown that the distribution of IQ scores in the population approximates a normal curve. Besides the Stanford-Binet, the most widely used intelligence testing device is the Wechsler scales, which in addition to assessing IQ also provides other verbal and nonverbal assessments. There are also intelligence tests that can be administered to groups of individuals, such as the SAT, which is used to predict success in college education. The SAT has been criticized for the possible effects of private coaching and gender bias. On the issue of intelligence testing, psychologists distinguish between aptitude tests, which are designed to predict an individual's ability to learn a skill, and achievement tests, which are designed to measure what has been learned.

Psychometrists specialize in psychological testing and work on issues such as the development, administration, and interpretation of the tests. Three concepts that are central to the work of psychometrists and that are very important in the testing of intelligence are validity, reliability, and standardization. Validity is the extent to which a test measures what it is intended to measure and includes content validity and criterion validity. Two types of criterion validity are concurrent validity and predictive validity. Reliability refers to the consistency of scores on a test. Standardization refers to the development of uniform procedures for the administration and scoring of a psychological test. Norms are established standards of performance on the test and are created by giving the test to a large group of individuals who are representative of the population.

Cultural fairness is a challenge in all psychological testing, but particularly important in intelligence testing, because of the possible consequences of scoring low in an intelligence test. Intelligence tests have a history of cultural bias that has resulted in extensive revisions of the tests. Two of the procedures that are done in order to make tests less culturally biased are to use questions that can be equally understood and applied by people from different cultures and socio-economic backgrounds and including questions that are not verbal, to assess the intelligence of people who do not understand the language of the test. The misuse of intelligence test scores can lead to stereotypes and unfair expectations. This information should be used with care and considered along with other psychological assessments, particularly in the academic setting.

Using the latest technology, research has uncovered various relationships between intelligence and brain characteristics and activity. Regarding the biological basis of intelligence, correlational studies have revealed that a larger brain size is associated with higher intelligence. It has also been found that individuals with higher intelligence process information faster than those with lower scores in traditional IQ tests. Another set of correlational studies has uncovered that high intelligence is associated with faster evoked potential, the electrical activity in the sensory area of the brain caused by external stimulation. Intelligence has also been associated with the patterns of consumption of glucose in the brain.

Psychologists have long debated whether intelligence is composed of one general ability or a number of specific abilities. Using the statistical procedure of factor analysis, Spearman developed the two-factor theory of intelligence, in which he proposed that there was a general (g) intelligence and a number of specific abilities (s). Thurstone also used factor analysis and concluded that there was not general intelligence; rather, he proposed a multiple-factor theory. According to Thurstone, intelligence consists of seven mental abilities: verbal comprehension, number ability, word fluency, spatial visualization, associative memory, reasoning, and perceptual speed. A recent classification of intelligence, proposed by Howard Gardner, includes eight types of intelligence: verbal skills, mathematical skills, spatial skills, bodily-kinesthetic skills, musical skills, interpersonal skills, intrapersonal skills, and naturalistic skills. Project Spectrum is a program designed to apply the principles of Gardner's theory in the classroom. Another multiple intelligences approach was developed by Robert Sternberg. Sternberg's triarchic theory emphasizes three essential components: analytical intelligence, creative intelligence, and practical intelligence. Sternberg's approach has also been applied to the classroom, where he recommends that instruction should be balanced with respect to the three types of intelligence. Salovy and Mayer have developed the concept emotional intelligence to refer to the interpersonal, intrapersonal, and practical aspects of intelligence. Goleman proposes that emotional intelligence involves four areas: emotional awareness, management of emotions, reading emotions, and handling relationships. The multiple intelligences approaches have been mostly criticized for taking the divisions of intelligence too far and possibly including abilities that are different from intelligence.

Extreme forms of intelligence include mental retardation and giftedness. Mental retardation is a condition of limited mental ability (usually an IQ of below 70) and difficulty in adaptive behavior. There are several classifications of mental retardation: mild, moderate, severe, and profound. The two main causes of mental retardation are organic, which involves genetic disorder or brain damage, and cultural-familial, involving no evidence of organic brain damage. A gifted individual has a well-above-average IQ and/or a superior talent in a certain area. There are three criteria describing gifted children: precocity, learning in qualitatively different ways than ordinary children, and a passion to master. While gifted people tend to be socially well adjusted and excel in their chosen careers, only a few become extremely creative and revolutionary in their domains of interest. This points out that there is a difference between intelligence and creativity. Creativity is the ability to think about something in a novel and unusual way and to come up with unconventional solutions to problems. Convergent thinking refers to producing one correct answer, and this is the type of thinking required in conventional intelligence tests. Divergent thinking, however, produces many answers to the same question and is more characteristic of creativity. The creative process can be organized in five steps: preparation, incubation, insight, evaluation, and elaboration; however, as might be expected, creative thinkers don't always follow the steps in order. Creative thinkers share several characteristics such as flexibility, inner motivation, risk taking, and objectively evaluating their creative work. Csikszentmihalyi recommends different ways in which we may all become more creative. Some of his recommendations are being open to new things every day, presenting others with new experiences every day, keeping notes of what surprises you, and following your interests.

There is very specific evidence of a genetic foundation for intelligence. Arthur Jensen has sparked debate with his thesis that intelligence is primarily inherited and that the differences in average intelligence between groups, races, nationalities, and social classes are therefore due to genetics. A concept used to figure out the extent to which intelligence is determined by genetics or the environment is heritability, which is a correlational statistic that indicates the fraction of the variance in IQ in a population that is attributed to genetics. The heritability of intelligence by late adolescence has been determined to be about .75, which reflects a strong genetic influence. An interesting observation is that heritability increases with age. Today's experts view intelligence as being determined by both genetics and the environment. Intelligence can be modified by providing an intellectually stimulating environment. In the controversial book, The Bell Curve, Herrnstein and Murray argue that a large underclass in America is developing that is unable to meet the needs of future employers. In response, psychologists have attempted to develop culture-fair tests since many early intelligence tests were culturally biased. Other debatable differences in intelligence are found when the scores of males are compared to the scores of females.