There is considerable disagreement concerning the age of onset and universality of attainment of Piaget's stage of formal operations. This study examines developmental differences in response to brief prompts in the use of a formal operational approach to the solution of two tasks. The subjects were 10 males and 10 females from each of Grades 5, 8, and 12. Three tasks requiring the formal operational skill of separating and testing variables were given to each subject. Results suggest that almost all the subjects could readily understand and utilize the approach of separating variables and testing each one while holding all others constant. Furthermore, the results support Piaget's claim that formal operations are available to nearly all normal young adults. Implications for the development of logical competence are discussed. (SJL)