Final answer:
Postformal thought is the approach to adult cognitive development that is an outgrowth of Piaget's theory.
Step-by-step explanation:
The approach to adult cognitive development that is an outgrowth of Piaget's theory is postformal thought.
Postformal thought is a stage of cognitive development that suggests there is a fifth stage beyond Piaget's formal operational thought. In postformal thought, adults integrate logic and emotion to make decisions based on situations and circumstances. They develop principles that depend on contexts and can handle emotionally charged issues.