Piaget's Formal Operational Stage

Characteristic Description Example
     
Hypothetico-deductive

reasoning

When faced with a problem, formal operational adolescents think of all possible factors that could affect the outcome, even those not immediately suggested by the concrete features of the situation. Then they try them out in a step-by-step fashion to find out which ones work in the real world. In biology class, Louis had to determine which of two fertilizers was best for growing African violets. Louis thought, "The kind of fertilizer might not be the only factor that's important. Its concentration and how often the plant is fed might also make a difference." Therefore, Louis planned an experiment in which each fertilizer would be applied in several strengths and according to different feeding schedules. He made sure to design the experiment so he could determine the separate effects of each factor on plant growth.
Propositional thought Formal operational adolescents can evaluate the logic of statements by reflecting on the statements themselves. They do not need to consider them against real-world circumstances. Louis was given the following propositional task and asked to indicate whether the conclusion was true, false, or uncertain.
  • Premise 1: All animals are purple.
  • Premise 2: A frobe is purple.
  • Conclusion: A frobe is an animal.

Louis concluded, correctly, that whether a frobe is an animal is uncertain. "A frobe might be an animal," he answered, "but it might also be a purple thing that is not an animal."