Who introduced the concept of a general factor of intelligence (g) and early form of factor analysis?

The concept of a general factor of intelligence, often referred to as "g," was introduced by Charles Spearman in the early 20th century. Spearman's work was foundational in the field of psychometrics and intelligence testing. He proposed that a single underlying factor, g, contributes to performance across various cognitive tasks. This idea emerged from his factor analysis studies, which demonstrated that individuals who perform well on one type of cognitive task tend to perform well on others, suggesting a common intelligence underlying various abilities.

Spearman’s approach involved statistical methods to analyze the correlations among different cognitive tests, leading him to conclude that such a general intelligence factor could be measured. His work laid the groundwork for many subsequent theories and assessments in intelligence research, influencing how intelligence has been understood and measured in psychology.