For centuries, people have been trying to define intelligence. However, a universally agreed upon definition proves to be elusive so far. To some, intelligence is the ability to acquire new information and to adjust to new circumstances, while others regard the skills to solve complex problems as more important. Thus, many contrasting theories have emerged. The four theories with the largest number of followers are the theory of general intelligence, the theory of primary mental abilities, the multiple intelligences theory, and the triarchic theory of intelligence.

General intelligence

The oldest theory is that of British psychologist Charles Spearman, who, at the beginning of the 20th century, proposed the existence of general intelligence. He observed that people's scores on different IQ tests tend to correlate. In other words, somebody who received a high score on one IQ test usually scored high on all other IQ tests, and vice versa. Therefore, he concluded that intelligence tests all measure one common factor, which he called general intelligence or “g”. In addition to that, Spearman argued that each test also measures some specific ability, which he termed “s" - vocabulary knowledge or mathematical skills, for example. However, what was of real importance to Spearman was general intelligence, which he believed to be the basis of all intellectual activities.

Crystallized and fluid intelligence

A similar theory by R. Cattell and J. Horn argues that there are two types of intelligence - fluid intelligence (gf) and crystallized intelligence (gc). Fluid intelligence is one's biological ability to reason and acquire new information. On the other hand, crystallized intelligence is the set of specific knowledge and abilities that an individual has acquired by learning and experience throughout his life (1).

Primary mental abilities

In 1938 American psychologist L. Thurstone suggested, that intelligence is composed of seven independent factors, which he called primary mental abilities:

1)verbal comprehension;

2)verbal fluency;

3)mathematical ability;

4)memory;

5)speed of perception;

6)reasoning skills;

7)spatial visualization (2).

Multiple intelligences

Similar to Thurstone's theory is that of Harvard psychologist Howard Gardner. In 1983, he proposed the existence of multiple intelligences, which are independent from each other. According to him, everybody possesses a certain combination of the following:

1)Linguistic intelligence;

2)Logical-mathematical intelligence;

3)Spatial intelligence;

4)Musical intelligence;

5)Bodily-kinesthetic intelligence;

6)Interpersonal intelligence;

7)Intrapersonal intelligence (3).

The Triarchic theory of intelligence

Finally, there is the Triarchic (three-part) theory of intelligence by R. Sternberg. According to him, there are three different types of intelligence. The first one is analytic intelligence, which is the ability to reason. It resembles the notion of general intelligence. The other component of intelligence, as defined by Sternberg, is creative intelligence or the ability to draw upon previous experience in order to solve new problems. The last part of intelligence, Sternberg argues, is practical intelligence, which reflects one's ability to deal with everyday situations (4).

In conclusion, no unified theory of intelligence has been proposed yet. Until that happens, the debates on what intelligence really is are bound to continue.

References:

1.Jensen, Arthur R. Straight Talk About Mental Tests. New York: The Free Press, 1981. 62-63.

2.Intelligence. Encarta Reference Library 2003. Microsoft Corporation, 2002.

3.Armstrong, Thomas. 7 kinds of smart: identifying and developing your multiple intelligences. New York: Plume, 1999.

4.Sternberg, Robert J. How practical and creative intelligence determines success in life. New York: Simon and Schuster, 1996.