From the 1920s to the 1960s, American psychologists primarily focused on the study of:

From the 1920s to the 1960s, American psychologists primarily focused on observable behavior, which is a hallmark of the behaviorist movement. This shift came in response to previous schools of thought, such as psychoanalysis and introspection, which emphasized internal mental processes that couldn't be directly observed.

Behaviorism, championed by figures like John B. Watson and B.F. Skinner, promoted the idea that psychology should be a science that studies only what can be seen and measured—namely, behaviors rather than thoughts or feelings. This focus on observable behavior allowed psychologists to use scientific methods to study and quantify behavior, leading to developments in areas such as conditioning and reinforcement.

During this period, other options like unconscious motives or cognitive processes were less emphasized. Psychoanalysis, though focused on unconscious motives, was often criticized for its lack of empirical support and scientific rigor compared to behaviorism. Cognitive psychology began to gain traction only after the 1960s, marking a gradual shift back toward exploring internal mental processes. Emotional responses, while acknowledged in various contexts, were not the central focus of psychological research during this era. Thus, the emphasis on observable behavior was the defining characteristic of psychology during this time frame.