What is the G factor? Spearman's Bifactorial Theory

What is the G factor? Spearman's Bifactorial Theory

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The g factor (also known as general intelligence, general mental ability or general intelligence factor) is a parameter or indicator of cognitive abilities and human intelligence.

The general intelligence A person basically refers to their ability to capture the environment, reason, solve problems and act efficiently and effectively in a given situation.

While we have different cognitive strengths and weaknesses, we all differ in the G factor, and valid IQ tests can give us a good measure of those individual differences.


  • 1 The G factor and Spearman's Bifactorial Theory
  • 2 The factor analysis of General Intelligence
  • 3 Discussion on General Intelligence

The G factor and Spearman's Bifactorial Theory

Charles Spearman first described the existence of general intelligence in 1904. According to Spearman, G factor is responsible for overall performance in mental ability tests. He noted that while people can certainly stand out and often excel in certain cognitive areas, those who get good scores in one area also tend to do so in other areas. For example, a person who has a good result on a verbal test will probably also score high on other tests.

He developed the theory called Bifactorial Theory, in which intelligence would consist of two fundamental parameters:

General Factor (G)

It refers to a eminently personal property, a specific property of the brain that varies from one individual to another, but remains stable over time.

Special Factor (S)

What represents the specific skills or aptitudes of a subject against a certain task, which varies depending on the previous education of the person and are not generalizable to other areas.

The factor analysis of General Intelligence

Charles Spearman also helped develop a statistical technique known as factor analysis. Factor analysis allows researchers to measure general skills through a series of different test elements.

Spearman believed that general intelligence represented a factor of intelligence underlying specific mental abilities. So, in intelligence tests, all tasks to be performed, whether related to verbal or mathematical skills, are influenced by the underlying G factor. For example, people who get good scores on questions that measure vocabulary also perform well on questions related to reading comprehension.

Thus, we could compare the concept of general intelligence with sport. A person can be a great swimmer, but this does not necessarily mean that he is also an excellent obstacle jumper. However, because this person is athletic and fit, they are likely to perform much better in other physical tasks than a less coordinated and more sedentary person.

The G factor explains the majority of individual differences in mental test performance. This is so regardless of the specific capacity that each test evaluates, the content of the test (whether words, numbers or figures) and the way in which the test is administered (in written or oral form, individually or in groups). Each concrete test of mental abilities measures certain competences, but they all reflect the G factor to some extent. Therefore, the G factor can be extracted from the scores of any battery of various tests.

Many intelligence tests, including that of Stanford-Binet, measure some of the cognitive factors that are believed to make up general intelligence. These include viso-spatial processing, mathematical logical reasoning, knowledge, fluid reasoning and working memory.

  • The viso-spatial processing It includes skills such as assembling puzzles and copying complex shapes.
  • The logical mathematical reasoning It implies the ability to solve problems with numerical factors.
  • The knowledge It is related to understanding about topics of various types.
  • The fluid reasoning It is based on the ability to think flexibly and solve problems.
  • The work memory It involves the use of short-term memory, as well as repeating lists of various elements.

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General Intelligence Discussion

Some researchers argue that the notion of general intelligence or G-factor is illusory, that there is no such global mental capacity and that the apparent "intelligence" is only a byproduct of one's opportunities to learn skills and information valued in a particular cultural context.

It is true that the concept of intelligence and the way in which individuals are classified according to this criterion, could have a very important social deviation. But the fact that the G factor is not specific to any particular domain of knowledge or mental ability suggests that it is independent of cultural content, including beliefs about what intelligence is. Further, the tests of different social groups reveal the same continuum of general intelligence.

Anyway, the notion that the intelligence of a person can be measured and summarized in a single number obtained through an IQ test, has been controversial for decades. Some psychologists, including Thurstone, challenged the concept of a G. Thurstone factor instead identified a quantity of what he called "primary mental abilities."

The most recent research points to the existence of an underlying mental capacity that contributes to good performance in different cognitive tasks. IQ scores, which are designed to measure this general intelligence, can predict academic success, but not life, as other factors such as childhood experiences, education, socioeconomic status, motivation, maturity and personality also play a critical role in determining overall success.

It may interest you:Difference between intelligence and Emotional Intelligence


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