Final answer:
The hallmark of postformal cognition is intellectual flexibility, which allows for context-dependent decision-making and integration of logic with emotion, contrasting with the more rigid thinking of previous cognitive stages.
Step-by-step explanation:
The hallmark of postformal cognition is intellectual flexibility. Postformal thinking involves making decisions based on situations and circumstances, integrating logic with emotion, and developing principles that are context-dependent. This is in contrast to formal operational thought in adolescents, where reasoning is more rigid and based solely on logical principles.
As opposed to Piaget's highest stage of cognitive development known as the formal operational stage, postformal thinking, as suggested by many developmental psychologists, incorporates the ability to approach decisions based on different situations and circumstances. Intellectual flexibility in this context means integrating logic with emotion, creating principles that rely on the context in which problems or issues arise. This contrasts with formal operations where thought patterns might be more rigid and abstract, and less influenced by emotional and contextual nuances.