Final answer:
Psychologist Charles Spearman theorized that a single factor, known as "g," contributes to all cognitive abilities.
Step-by-step explanation:
Psychologist Charles Spearman theorized that a single factor, known as "g," contributes to all cognitive abilities. According to Spearman's theory, intelligence is not made up of multiple unrelated types, nor is it best explained by multiple factors. Instead, Spearman proposed that there is a common factor, g, that underlies all different cognitive abilities. This means that someone who performs well in one area of cognitive ability is likely to perform well in other areas as well, and vice versa.