Final answer:
The correct answer is c) relativistic thinking, which represents the ability of an adult to make decisions based on situational contexts, integrating logic with emotion, and recognizing multiple viewpoints, which is indicative of postformal cognitive development.
Step-by-step explanation:
The ability that is a hallmark of adult adaptive thought from the options provided is c) relativistic thinking. Relativistic thinking is a concept introduced as part of postformal cognitive development. It suggests that adults, unlike adolescents, make decisions by integrating logic and emotion, and they do so based on the specific situations and circumstances they encounter. This type of thinking is more fluid and adaptable than the fixed, concrete operational thought usually observed in children. Whereas formal operational thought, evident in adolescence, involves the ability to handle abstract and hypothetical situations, relativistic thinking goes beyond to acknowledge that truth may vary depending on the perspective or context. An adult in postformal thought will appreciate that there can be multiple valid viewpoints, and thus their thinking is not as absolute as it is in adolescents who are in the formal operational stage of cognitive development.
Relativistic thinking is part of the postformal stage, which is characterized by understanding that life is not always black and white, and it allows for nuances and grey areas in thinking and decision making. It stands in contrast to functional fixedness, which can prevent an individual from seeing all the potential solutions to a problem by considering only traditional approaches. Instead, relativistic thinking enables adults to adapt their cognitive process to real-world complexities, reflecting a more mature level of cognitive development.