Step 1: Understand the definition of psychology by breaking down the term into its roots: 'psyche' meaning mind or soul, and 'logy' meaning study of.
Step 2: Recognize that psychology is a scientific discipline focused on understanding both observable behaviors and internal mental processes.
Step 3: Differentiate psychology from other fields such as history (study of historical events), medicine (diagnosing physical illnesses), and psychoanalysis (interpreting dreams and symbols).
Step 4: Identify that the correct description of psychology is the 'scientific study of behavior and mental processes' because it involves systematic research and empirical methods.
Step 5: Conclude that psychology is not just about subjective interpretation or physical health, but about applying scientific methods to understand how people think, feel, and act.