- g (Spearman's g, General intelligence) : g is the term introduced by Charles Spearman to describe his concept of a general intelligence. It is Spearman’s abbreviation for Neogenesis, which means one’s ability to understand relations or general mental ability. In Psychometric theory, it is the idea that intelligence can be expressed in terms of a single factor, general intelligence or g, first formulated by Spearman in the early 1900s.