Overview of the Theories of Intelligence

Intelligence theories
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What exactly is intelligence? How do researchers define and measure this mental quality? While intelligence is one of the most talked about subjects in psychology, there is no standard definition of what exactly constitutes "intelligence." Some researchers have suggested that intelligence is a single, general ability while others believe that intelligence encompasses a range of aptitudes, skills, and talents.

How Do Psychologists Define Intelligence?

Intelligence has been an important and controversial topic throughout psychology's history. Despite the substantial interest in the subject, there is still considerable disagreement about what exactly constitutes intelligence. In addition to questions of exactly how to define intelligence, the debate continues today about whether accurate measurements are even possible.

At various points throughout recent history, researchers have proposed some different definitions of intelligence. While these definitions can vary considerably from one theorist to the next, current conceptualizations tend to suggest that intelligence involves the ability to:

  • Learn: The acquisition, retention, and use of knowledge is an important component of intelligence.
  • Recognize problems: To put knowledge to use, people must first be able to identify possible problems in the environment that need to be addressed.
  • Solve problems: People must then be able to take what they have learned to come up with a useful solution to a problem they have noticed in the world around them.

Intelligence involves some different mental abilities including logic, reasoning, problem-solving, and planning. While the subject of intelligence is one of the largest and most heavily researched, it is also one of the topics that generate the greatest controversy.

While psychologists often disagree about the definition and causes of intelligence, research on intelligence plays a significant role in many areas. These include decisions regarding how much funding should be given to educational programs, the use of testing to screen job applicants, and the use of testing to identify children who need additional academic assistance.

So where does intelligence come from? How do we measure it? Psychologists have pondered these questions for years, yet the answers remain the subject of considerable debate.

A Background on Intelligence

The term "intelligence quotient," or IQ, was first coined in the early 20th century by a German psychologist named William Stern. Psychologist Alfred Binet developed the very first intelligence tests to help the French government identify schoolchildren who needed extra academic assistance. Binet was the first to introduce the concept of mental age or a set of abilities that children of a certain age possess.

Since that time, intelligence testing has emerged as a widely used tool that has led to developing many other tests of skill and aptitude. It, however, continues to spur debate and controversy over the use of intelligence tests, cultural biases, influences on intelligence, and even the very way we define intelligence.

Theories of Intelligence

Different researchers have proposed a variety of theories to explain the nature of intelligence. The following are some of the major theories of intelligence that have emerged during the last 100 years.

Charles Spearman: General Intelligence

British psychologist Charles Spearman (1863–1945) described a concept he referred to as general intelligence or the g factor. After using a technique known as factor analysis to examine some mental aptitude tests, Spearman concluded that scores on these tests were remarkably similar. People who performed well on one cognitive test tended to perform well on other tests while those who scored badly on one test tended to score badly on others.

He concluded that intelligence is general cognitive ability that could be measured and numerically expressed.

Louis L. Thurstone: Primary Mental Abilities

Psychologist Louis L. Thurstone (1887–1955) offered a differing theory of intelligence. Instead of viewing intelligence as a single, general ability, Thurstone's theory focused on seven different "primary mental abilities." The abilities that he described were:

  • Verbal comprehension
  • Reasoning
  • Perceptual speed
  • Numerical ability
  • Word fluency
  • Associative memory
  • Spatial visualization

Howard Gardner: Multiple Intelligences

One of the more recent ideas to emerge is Howard Gardner's theory of multiple intelligences. Instead of focusing on the analysis of test scores, Gardner proposed that numerical expressions of human intelligence are not a full and accurate depiction of people's abilities. His theory describes eight distinct intelligences based on skills and abilities that are valued in different cultures.

The eight intelligences Gardner described are:

  • Visual-spatial Intelligence
  • Verbal-linguistic Intelligence
  • Bodily-kinesthetic Intelligence
  • Logical-mathematical Intelligence
  • Interpersonal Intelligence
  • Musical Intelligence
  • Intrapersonal Intelligence
  • Naturalistic Intelligence

Robert Sternberg: Triarchic Theory of Intelligence

Psychologist Robert Sternberg defined intelligence as "mental activity directed toward purposive adaptation to, selection and shaping of, real-world environments relevant to one's life." While he agreed with Gardner that intelligence is much broader than a single, general ability, he instead suggested some of Gardner's intelligences are better viewed as individual talents. Sternberg proposed what he referred to as "successful intelligence" involving three different factors:

  • Analytical intelligence: This component refers to problem-solving abilities.
  • Creative intelligence: This aspect of intelligence involves the capacity to deal with new situations using past experiences and current skills.
  • Practical intelligence: This element refers to the ability to adapt to a changing environment.

Questions About Intelligence Testing

In order to gain a deeper understanding of intelligence and the tests that have been developed in an attempt to measure this concept, it is important to understand the history of intelligence testing, the scientific research that has been conducted, and the findings that have emerged.

Major questions about intelligence and IQ testing still include:

  • Is intelligence a single ability, or does it involve an assortment of multiple skills and abilities?
  • Is intelligence inherited, or does the environment play a larger role?
  • Are intelligence tests biased?
  • What do intelligence scores predict, if anything?

To explore these questions, psychologists have conducted a considerable amount of research on the nature, influences, and effects of intelligence.

A Word From Verywell

While there has been considerable debate over the exact nature of intelligence, no definitive conceptualization has emerged. Today, psychologists often account for the many theoretical viewpoints when discussing intelligence and acknowledge that this debate is ongoing.

You can start by learning more about some of these questions and discoveries.

Gardner, H. (1983). Frames of mind: The theory of multiple intelligences. New York: Basic Books.
Spearman, C. (1904). "General intelligence," objectively determined and measured. American Journal of Psychology 15, 201-293.
Sternberg, R. J. (1985). Beyond IQ: A Triarchic Theory of Intelligence. Cambridge: Cambridge University Press.
Thurstone, L.L. (1938). Primary mental abilities. Chicago: University of Chicago Press.