How did Spearman develop his two-factor theory?

According to Spearman, intelligence is a general cognitive ability that can be measured and numerically expressed. He feels that humans possess a single underlying factor “a generalized form of intelligence”, known as the g-factor, which helps them to utilize corresponding abilities “a specialized form of intelligence”, known as the s-factor. Spearmen linked this relationship to a common factor, called the General Intelligence (g). Thus, this theory came to be known as the Two-Factor Theory of Intelligence. IQ or intelligence quotient tests, which is a technique of measuring one’s general cognitive abilities, is the outcome of Spearman’s theory of General Intelligence. Read More>> Spearman’s theory of General Intelligence