Final answer:
Psychology influenced probation officers in the 1940s to emphasis therapeutic counseling over moral leadership, reflecting the integration of social science with professional practices.
Step-by-step explanation:
By the 1940s, the development of psychology as a field of social science research led probation officers to shift their emphasis from moral leadership to therapeutic counseling. Psychology began to influence various aspects of social services and justice systems, including the role of probation officers who incorporated therapeutic techniques into their work with clients. This reflects a broader historical trend of social sciences impacting professional practices and illustrates how advances in understanding human behavior can lead to changes in social roles and institutions.