The Behavioral school of thought has been a powerful one spanning the decades of the 1920s into the 1990s. Although the school of thought is not as organized today, its principles are still a powerful influence on psychological thought and practice. Its main tenet was that the environment is the main, and some thought only, influencer of behavior. This brings to mind the nature/nurture issue as to whether our biological endowment (our genetic structure) or the environment causes us to do what we do. What do you think? We see schools of thought vary on this question and certainly, the idea of eugenics was the extreme of the "nature" side of the issue.