Spearman concluded that there is a single g-factor which represents an individual’s general intelligence across multiple abilities, and that a second factor, s, refers to an individual’s specific ability in one particular area (Spearman, as cited in Thomson, 1947). In other words, there was a strong correlation between performing well in math and music, and Spearman then attributed this relationship to a central factor, that of general intelligence (g).

In the case of intelligence, Spearman noticed that those who did well in one area of intelligence tests (for example, mathematics), also did well in other areas (such as distinguishing pitch Kalat, 2014). To arrive at this theory, Spearman used a technique known as factor analysis.įactor analysis is a procedure through which the correlation of related variables are evaluated to find an underlying factor that explains this correlation.

That, according to Spearman, underlies multiple specific skills, including verbal, spatial, numerical and mechanical.Ĭharles Spearman, an English psychologist, established the two-factor theory of intelligence back in 1904 (Spearman, 1904). General intelligence, also known as g factor, refers to a general mental ability Psychologists contend that intelligence is genetic, or inherited, and others claim that it is largely influenced by the surrounding environment.Īs a result, psychologists have developed several contrasting theories of intelligence as well as individual tests that attempt to measure this very concept. Some researchers argue that intelligence is a general ability, whereas others make the assertion that intelligence comprises specific skills and talents. Galton’s study of intelligence in the laboratory setting and his theorization of the heritability of intelligence paved the way for decades of future research and debate in this field. Operationalization is an important process in research that involves defining an unmeasurable phenomenon (such as intelligence) in measurable terms (such as reaction time), allowing the concept to be studied empirically (Crowthre-Heyck, 2005). Thus, Galton operationalized intelligence as reaction time. Galton theorized that because quickness and other physical attributes were evolutionarily advantageous, they would also provide a good indication of general mental ability (Jensen, 1982). Galton was interested in the concept of a gifted individual, so he created a lab to measure reaction times and other physical characteristics to test his hypothesis that intelligence is a general mental ability that is a produce of biological evolution (hello, Darwin!). The study of human intelligence dates back to the late 1800s when Sir Francis Galton (the cousin of Charles Darwin) became one of the first people to study intelligence.

Reliable intelligence test