Growing out of a child’s cognitive developmental history, formal operations become established at Cognitive development about the age of 12–15 years. Reflected in his ability to reason Adolescence hypothetically and independently on concrete states of affairs, these structures may be represented by reference to Logic combinatorial systems and to 4-groups. The essence of the Environmental differences logic of cultured adults and the basis for elementary scientific Individual differences thought are thereby provided. The rate at which a child progresses through the developmental succession may vary, especially from one culture to another. Different children also vary in terms of the areas of functioning to which they apply formal operations, according to their aptitudes and their professional specializations. Thus, although formal operations are logically independent of the reality content to which they are applied, it is best to test the young person in a field which is relevant to his career and interests.