Why was William McDougall's theory not well known?

William McDougall's theory, particularly his ideas on social psychology and instinct theory, did not gain widespread recognition due to several factors. His work was overshadowed by the rise of behaviorism in the early 20th century, which emphasized observable behavior over introspective methods and instinctual explanations. Additionally, McDougall's concepts were often seen as overly abstract and lacking empirical support, leading to skepticism among contemporary psychologists. As a result, his contributions were largely marginalized in favor of more empirically grounded theories.