Intelligence: concepts, theories, and applications

Intelligence is a general mental capability that involves the ability to reason, plan, solve problems, think abstractly, comprehend ideas and language, and learn (Intelligence). Some researchers such as Charles Spearman have proposed that intelligence is a single quantity or concept, but others such as Howard Gardner assert that intelligence really consists of a set of relatively independent abilities. While there is much debate over the validity of the two theories, Spearman's theory of intelligence is more accepted by psychology today.

According to Spearman's two-factor theory of intelligence, the performance of any intellectual act requires some combination of "g," a general intellectual ability which is available to the same individual to the same degree for all intellectual acts, and of "specific factors" or "s" which are specific to that act and which varies in strength from one act to another (Charles Spearman, Human Intelligence). Spearman concludes that the most important information to determine a person's intellectual ability is an estimate of their "g" because it pervades all tasks.

In sharp contrast to Spearman's theory of intelligence, Gardner developed the theory of multiple intelligences that suggests that there a significant number of distinct forms of intelligence that each individual possesses in varying degrees (Multiple intelligences). Gardner identified seven primary forms: linguistic, musical, logical-mathematical, spatial, body-kinesthetic, intrapersonal (e.g., insight, metacognition) and interpersonal (e.g., social skills). Gardner also emphasizes the cultural context of multiple intelligences, stating the different cultures tend to emphasize particular intelligences.

While the definition and importance of intelligence is somewhat controversial, the concept of a single dominant factor of intelligence, general mental ability or "g," is accepted by most psychology experts according to an American Psychological Association task force report issued in 1995. (Gottfredson, 1998). The reason is that there is sufficient psychometric and biological evidence to prove that the "g" factor actually exists (Gottfredson, 2004). And, "g's" predictive validity has been repeatedly demonstrated in predicting non-acadmic outcomes. For example, Campbell found in work published in 1990 that "g" plays a substantial role in performing jobs well and Jencks in 1979 and Murray in 1998 reported that "g" greatly influences getting ahead socioeconomically (Gottfredson, 2004).