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As long as opportunities for learning are available, crystallized intelligence can increase indefinitely during a person's life. Crystallized intelligence, on the other hand, is the knowledge and skills obtained through learning and experience. Measures of fluid intelligence, such as speed of reasoning and memory, increase into adulthood and then decline due to the aging process. Fluid intelligence represents the biological basis of intelligence. 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). 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. 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.
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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.
#Mental age divided by chronological age series#
Each of the tests consists of a series of 10 or more subtests. 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). Most modern tests arbitrarily define the average score as 100. These tests give a score that reflects how far the person's performance deviates from the average performance Researchers using this approach believe that intelligence can be measured through the administration of various forms of IQ tests. The dominant method of studying intelligence in this century has been the psychometric approach. Scored a mental age of 9, she would be assigned an IQ of 150 ((9/6)x100) 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). It would exceed chronological age in bright children and would be below in those of lesser ability. 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. 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. 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). Francis Galton was among the first to measure individual differences in intellectual abilities.