Discover your intellectual strengths
Francis Galton was among the first to measure individual differences in intellectual abilities. Based on quantitative studies of prominent individuals and their family trees, he concluded that intellectual ability is inherited in much the same way as physical traits, and he later published his findings in Hereditary Genius (1869). Eventually, Galton modified his original theories to recognize the effects of education and other environmental factors on mental ability, although he continued to regard heredity as the preeminent influence.
Galton's work was followed in 1905 by that of French psychologist Alfred Binet, who introduced the concept of mental age, which would match chronological age in children of average ability. It would exceed chronological age in bright children and would be below in those of lesser ability. Binet's test was introduced to the United States in a modified form in 1916, and with it the concept of the intelligence quotient (mental age divided by chronological age and multiplied by 100). For example, if a 6-year-old girl scored a mental age of 9, she would be assigned an IQ of 150 ((9/6)x100)
The dominant method of studying intelligence in this century has been the psychometric approach. Researchers using this approach believe that intelligence can be measured through the administration of various forms of IQ tests. These tests give a score that reflects how far the person's performance deviates from the average performance of others who are the same age. Most modern tests arbitrarily define the average score as 100.
The most widely used modern tests of intelligence are the Stanford-Binet, the Wechsler Intelligence Scale for Children (WISC), the Wechsler Adult Intelligence Scale (WAIS), and the Kaufman Assessment Battery for Children (Kaufman-ABC). Each of the tests consists of a series of 10 or more subtests. Subtests are sections of the main test in which all of the items are similar. Examples of subtests include vocabulary ("Define happy"), similarities ("In what way are an apple and pear alike?"), digit span (repeating digit strings of increasing length from memory), information ("Who was the first president of the United States?"), object assembly (putting together puzzles), mazes (tracing a path through a maze), and simple arithmetic problems.
Whatever the nature of the IQ test, many researchers believe that a general statistical factor can be extracted from the results of multiple IQ tests mainly due to the fact that people who perform well on one type of intelligence test tend to do well on others also. Charles Spearman named the general mental ability that carried over from one test to another "g" for general intelligence, and decided that it consisted mainly of the ability to infer relationships based on one's experiences.
In the 1960s American psychologists Raymond Cattell and John Horn applied new methods of factor analysis and concluded there are two kinds of general intelligence: fluid intelligence (gf) and crystallized intelligence (gc). Fluid intelligence represents the biological basis of intelligence. Measures of fluid intelligence, such as speed of reasoning and memory, increase into adulthood and then decline due to the aging process. Crystallized intelligence, on the other hand, is the knowledge and skills obtained through learning and experience. As long as opportunities for learning are available, crystallized intelligence can increase indefinitely during a person's life. For example, vocabulary knowledge is known to increase in college professors throughout their life span.
Another approach is Howard Gardner's theory of multiple intelligences, which replaces the general intelligence factor (g ) with seven different types of intelligence: linguistic; logical-mathematical; spatial; interpersonal (ability to deal with other people); intrapersonal (insight into oneself); musical; and bodily-kinesthetic (athletic ability). According to Gardner, each of these areas of competence includes a separate set of problem-solving skills that can be mobilized by various symbolic systems. Every person has all the different types of intelligence, although some may be developed far more fully than others. (The most dramatic example of this is found in savants, mentally retarded people with exceptional abilities in a few highly specialized areas, usually involving calculations.)
In the 1980s American psychologist Robert Sternberg proposed a theory of intelligence that, like Gardner's theory of multiple intelligences, attempted to expand the traditional conception of intelligence. Sternberg noted that mental tests are often imperfect predictors of real-world performance or success. People who do well on tests sometimes do not do as well in real-world situations. According to Sternberg's triarchic (three-part) theory of intelligence, intelligence consists of three main aspects: analytic intelligence, creative intelligence, and practical intelligence. These are not multiple intelligences as in Gardner's theory, but interrelated parts of a single system. Thus, many psychologists regard Sternberg's theory as compatible with theories of general intelligence.
The statistics gathered from this test reveal the following interesting facts.
Leonardo Da Vinci Artist, Inventor 220 IQ
Voltaire Writer 190 IQ
Garry Kasparov Chess grandmaster 190 IQ
Galileo Galilei Physicist/Astronomer 185 IQ
Immanuel Kant Philosopher 175 IQ
Plato Philosopher 170 IQ
Charles Darwin Naturalist 165 IQ
Wolfgang Amadeus Mozart Composer 165 IQ
Albert Einstein Physicist 160 IQ