At this point, I think that psychologists study human behaviour, and by extension, the human mind. Psychologists may also study the behaviour of animals, in some cases, to better understand of human behaviour. Psychologists are tasked to answer questions such as, why people act in certain ways, when in certain situations, why do people feel emotion, how does memory work, etc. I also think that psychologists study the illness of the mind. I believe that psychologists better their understanding of human behaviour and the human mind through theory and experimentation, rather than through the study of biological systems.