In which year did Spearman first describe the existence of general intelligence?

Spearman first described the concept of general intelligence, often referred to as "g," in the year 1904. In his work, he introduced this idea to explain the correlation observed among various cognitive tasks, suggesting that these commonalities stemmed from a general underlying intelligence. His research laid the foundational framework for understanding intelligence as a singular, general ability, which would significantly influence the field of psychology and the study of intelligence for years to come. This early work distinguished itself by presenting a systematic approach to analyzing intellectual abilities through statistical methods, setting the stage for future theories of intelligence.