Maslow's critique developed in the 1940s in the context of his theory of self-actualization, viewing human behavior as the result not only of 'a link between stimulus and response, but also a combination of feelings, attitudes and wishes that constitute the personality as a whole (Maslow, 1968). Rollo May believes that behaviorism was wrong when it asserted that the self did not exist and that all behavior was conditioned. He later stated that human beings are not rats and cannot be studied and understood in the same way (May 1969). May viewed humans as having the ability to choose while rats lacked the ability to perform higher mental functions that involve free will. Maslow further added to May's response, that behaviorists only see the animal aspects of human nature, precisely because he focuses on adaptive behavior (May, 1969). Carl Rogers led to further criticism by stating that there is purpose and choice in human action, which is what Skinner had stated in contrast (Rogers,