Theories of intelligence deal with the foundation and structure of intelligence. One of the key questions is whether there is one or several forms of intelligence. C. Spearman suggested that humans have a domain-general ability, the g-factor, as well as some more specific abilities, s-factors. The g is the common factor in all subtests on intelligence tests, and Spearman maintains that the g-factor is most important to assess. The standard measure of intelligence is the intelligence quotient. More theories emphasize the role of intelligence in adapting, learning, using skills and coping in a particular environment. Sternberg’s model of intelligence comprises three parts, or sub theories: process, experience and adaptation, which is why it is called triarchic. Internationally there exists a large number of standardized tests that measure intellectual functioning in children and adolescents, and rank their performance in relation to their peers.