The formal operational stage is the fourth and final stage in Piaget'stheory. It begins at approximately 11 to 12 years of age, and continuesthroughout adulthood, although Piaget does point out that some people may neverreach this stage of cognitive development.

The formal operational stage is characterized by the ability to formulatehypotheses and systematically test them to arrive at an answer to a problem.

The individual in the formal stage is also able to think abstractly and tounderstand the form or structure of a mathematical problem.

Another characteristic of the individual is their ability to reason contraryto fact. That is, if they are given a statement and asked to use it as thebasis of an argument they are capable of accomplishing the task. For example,they can deal with the statement "what would happen if snow were black".