How the Concept of Intelligence Developed

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.2

Since that time, intelligence testing has emerged as a widely used tool that has led to developing many other tests of skill and aptitude. However, it continues to spur debate and controversy over the use of such testing, cultural biases that may be involved, 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. Here 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 a general cognitive ability that can be measured and numerically expressed.3

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 include:

  • Verbal comprehension
  • Reasoning
  • Perceptual speed
  • Numerical ability
  • Word fluency
  • Associative memory
  • Spatial visualization
Annals of Human Biology
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