The Investment theory (Cattell, 1987) states that learning in different fields is dependent on a general ability to reason in novel situations (Gf), and that development of knowledge and skill therefore is influenced by Gf, among other things. The Encapsulation theory (Gustafsson & Carlstedt,2006) makes the inference that Gf is encapsulated in measures of General Crystallized intelligence(Gc) and that information about Gf therefore does not add to prediction of further learning. The purpose of the present study was to investigate the effects of Gf and Gc on knowledge acquisition indifferent subjects in school. In all 9002 individuals from the Evaluation Through Follow-up longitudinal database were included. A path model was fitted to measures of Gf and Gc. Results showed that Gf had influence on measures of early and late Gc. However, there were no additional effects of Gf on subject grades, which was interpreted as providing partial support for the Encapsulation theory.