- 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.