Psychologists have been debating the definition and the theory of intelligence for many years. One dictionary defines intelligence as "the ability to learn or understand or to deal with new or trying situations; the ability to apply knowledge to manipulate one's environment or to think abstractly as measured by objective criteria." Different theories exist that try to determine what qualities are a part of intelligence. Two psychologists, Charles Spearman and Howard Gardner, have their own theories about determining what intelligence is and how to measure it.
In the early 1900s, Charles Spearman (1863-1945) made an important observation that has influenced many later theories of intelligence: He noted that all tests of mental ability consisted of positive correlation, or the degree to which two variables are associated and vary together (Intelligence, 2006). Spearman reasoned that there must be a common variable or factor producing these positive correlations. He developed a statistical method, called factor analysis, to show the underlying factor involved in the positive correlations.
Based on this factor analysis, the two-factor theory of intelligence was discovered. Spearman called the first factor general intelligence or the general factor, or simply as g. According to Spearman, g is the single basis for all intellectual tasks and cognitive abilities and is what all of the mental tests had in common. The second factor was identified as the specific factor, or s. The specific factor related to an individual mental task: the individual abilities that would make a person more skilled at one cognitive task than another (general intelligence factor, 2006). Throughout his life, Spearman argued that g was really what scientist should mean by intelligence. He suggested that g measured a mental "power" or "energy" (Intelligence, 2006).
However, Dr. Howard Gardner (1943- ), a professor of education...