Final answer:
Behaviorists rejected cognitivism because they believed in studying only directly observable behavior, not internal mental processes, as they considered the mind a 'black box'.
Step-by-step explanation:
Behaviorists rejected cognitivism because they did not see any value in studying something that was not directly observable. This core tenet of behaviorism is encapsulated by the idea that psychology should be an objective science, focusing solely on overt behavior and minimizing the role of internal mental processes. John Watson and B.F. Skinner, prominent figures in behaviorism, viewed the internal workings of the mind—cognitive processes—as secondary or even irrelevant to understanding behavior. Skinner considered the mind a "black box", unknowable and not worthy of scientific study, a perspective that starkly contrasted with Edward C. Tolman's work, which indicated a cognitive aspect to learning. Tolman found through his experiments with rats that cognition played a role in learning, especially evident in latent learning where learning occurs without immediate reinforcement.