Exploring the G-Factor in Intelligence

Intelligence has always been a fascinating topic for psychologists and scientists alike. Among the many theories that attempt to explain it, one concept stands out: the G-factor, also known as general intelligence or the general factor, introduced over a century ago. But what exactly is the G-factor? What are its components, and how many types of general intelligence are there? Keep reading to explore the answers & learn other details about the G-factor!

What is General Intelligence (G-factor)?

General intelligence, or the G-factor (“general factor”), refers to a broad cognitive capacity that affects an individual’s performance across various intellectual tasks.

This general mental ability is often described as what underlies specific cognitive skills in areas like verbal, numerical, visual-spatial, and mechanical abilities. In other words, general intelligence can be considered a construct made up of various cognitive skills that allow us to gain knowledge and solve problems in life.

Here, it’s worth noting that, in fact, common terms like general cognitive ability, IQ (intelligence quotient), or general mental ability are often used interchangeably to refer to general intelligence.

Charles Spearman’s Theory of General Intelligence

The G-factor was first introduced by Charles Edwards Spearman in the early 20th century. In 1904, he proposed that this G-factor accounted for overall performance on cognitive ability assessments. He noted that while individuals could excel in specific areas, those who performed well in one area often tended to perform well across other areas as well.

In his two-factor theory, sometimes referred to as the general intelligence theory or the two-factor theory of intelligence, Spearman proposed that intelligence is made up of two factors: the g factor and the s factor, and that "g" or g-factor (general intelligence) is correlated with “s” or s-factor (specific abilities) to some extent. All tasks on intelligence tests, whether they assess verbal or mathematical skills, were influenced by the underlying "g" factor.

Today, a large part of IQ tests is based on factor models derived from Spearman’s work on the g-factor. For instance, the Stanford-Binet test evaluates various aspects of performance, such as working memory and visual-spatial reasoning, which collectively contribute to general intelligence.

Components of General Intelligence

In fact, general intelligence is not a singular construct. Instead, it’s believed to comprise different cognitive abilities that work together, including:

• Fluid reasoning: The capacity to think flexibly and address problems.
• Knowledge: This involves a broad, general understanding of various topics, closely associated with crystallized intelligence.
• Quantitative reasoning: This relates to the ability to solve numerical problems and work effectively with numbers.
• Visual-spatial processing: This refers to skills in interpreting and manipulating visual information, such as assembling puzzles. 
• Working memory: This involves the ability to use short-term memory effectively, like recalling and repeating a list of items.

IQ Testing and How General Intelligence is Measured

Modern intelligence tests often assess various cognitive factors believed to contribute to general intelligence. These tests propose that intelligence can be assessed and expressed by a number, like the IQ score.

As previously mentioned, the Stanford-Binet Intelligence Scales, one of the most widely recognized IQ tests, serves as a good example of an intelligence assessment that aims to evaluate the G-factor. It assesses a range of cognitive abilities, from quantitative reasoning to working memory, fluid reasoning, and more.

Along with an overall IQ score, the test’s latest edition (the 5th edition) also provides composite scores and subtest scores across 10 areas. According to the Stanford-Binet 5th Edition (SB5) classification, an IQ score between 90 and 109 is considered “average,” scores from 120 to 129 are deemed “superior,” and those above 145 are classified as “very gifted.”

In addition to the Stanford-Binet, many other assessments, such as the Wechsler Adult Intelligence Scale (WAIS), also assess a range of cognitive skills and a person’s intellectual potential through standardized scores.

Impact of General Intelligence

Although the concept of intelligence remains a topic of debate in psychology, researchers believed that g matters and general intelligence is linked to overall life success. Some of the impacts that the G-factor may have can be seen in areas like:

• Academic Success: General mental ability strongly correlates with performance in school and higher education. Still, it’s worth noting that some research also suggests that about 51%-75% of success and achievement can’t be determined by the g alone. That means while it does affect one’s academic performance, other factors also matter.
• Career Achievement: High IQ scores have long been believed to correlate with job success. For occupations or professions with a higher degree of complexity, the g-factor becomes more important for career achievements. Also, it’s essential to know that not just general intelligence but also specific abilities play a vital role in job attainment, according to a 2020 study.
• Health and Longevity: Intelligence can have an effect on a person’s health, just as health can influence intelligence. It’s believed that higher intelligence is associated with better decision-making and healthier lifestyle choices, contributing to longer lifespans.

In addition to the above areas, intelligence can affect other life aspects, such as problem-solving, income, and more.

Spearman’s Theory and Other Intelligence Theories

While Spearman's theory of general intelligence focuses on the G-factor, some other theories of intelligence propose and emphasize multiple intelligences. These include Howard Gardner’s Theory of Multiple Intelligences, Robert Sternberg’s Triarchic Theory, and Thurstone's Primary Mental Abilities.

• Howard Gardner’s Theory of Multiple Intelligences: In the theory, Gardner proposed that intelligence isn’t a single entity but a collection of independent intelligences, such as linguistic, spatial, interpersonal, logical-mathematical, musical intelligences, and more.
• Robert Sternberg’s Triarchic Theory: The theory highlights three types of intelligence: analytical, creative, and practical abilities, all necessary for successful intelligence.
• Thurstone's Primary Mental Abilities: Unlike the G-factor, this theory doesn’t assume a single underlying ability. Thurstone identified a set of cognitive skills he called primary mental abilities, which include associative memory, reasoning, verbal comprehension, number facility, and more. Thurstone suggested that everyone possesses these abilities to some extent, but their levels can vary. Individuals may excel in certain areas while showing lower aptitude in others.
• Fluid and Crystallized Intelligence (Cattell): Raymond Cattell expanded on the G-factor by dividing intelligence into Gf, or fluid intelligence (problem-solving and adaptability), and Gc, crystallized intelligence (knowledge and skills gained through experience).

In conclusion, the g-factor, or general intelligence factor, provides a valuable framework for understanding human intelligence. It highlights the correlation among cognitive abilities and emphasizes the importance of a broad range of mental capacities. However, it’s also important to note that while influential, the g-factor is not without controversies; some researchers argue that no single underlying factor can fully account for the positive correlation observed among cognitive abilities. So, the g factor should be just one way of thinking about mental capacity and intelligence.