The answer is an experimental science.
While social psychology does involve observations of human behavior, this alone does not set it apart from other ways of interpreting social behavior, such as folk wisdom or literature. Observations are a part of many disciplines, including those that are not scientific.
Social psychology is distinguished from other interpretations of social behavior because it relies on the scientific method, including controlled experiments, to test hypotheses about social behavior. This experimental approach allows for the systematic and objective investigation of social phenomena, which is a key characteristic that sets it apart from folk wisdom or literature.
Although social psychology does involve the development and testing of theories, this is not unique to the field. Many disciplines, including literature and philosophy, also develop and use theories to understand human behavior.
While objective measurement is a crucial aspect of social psychology, it is not the sole characteristic that sets it apart. Other fields, such as natural sciences, also rely on objective measurement. The combination of objective measurement with experimental methods is what truly distinguishes social psychology.