Behaviour: Helping another person – a directly observable action
Thought: Planning a series of moves requires cognitive work or mental concentration
Feeling: Frustration or exasperation involves an emotion or affect
Psychology is generally defined as the scientific study of behaviour and mental states.
It helps to pull a definition like this apart and use different words to explain it.
“Behaviour” can be described as observable actions that can be seen, monitored or measured.
“Mental states” refer to internal and subjective experiences: the thoughts and feelings that make up the inner landscape of the mind. Unlike behaviour, thoughts and feelings are not directly observable. They may be reported by the person or inferred from a person’s behaviour. This is not always easy or straightforward.
The picture on the left, for instance, shows a teenager rolling her eyes. This is a behaviour that can be observed directly. A parent or teacher could even develop a checklist of defiant teenager behaviours and count how many are observed in the course of a week.
Interpreting which mental state underlies this behaviour, however, is much more complex. You could ask the person herself, who might or might not be able to explain her eye-roll. You could infer that she is irritated, amused or embarrassed (these are all mental states, usually considered to be feelings). You might conclude that she believes whatever someone has just said or done is silly or exasperating (this is another mental state, usually considered to be a thought).
“Scientific study” in the definition of psychology refers to an objective and systematic approach to investigating behaviour and mental states. A science is based on neither guessing nor intuition, but rather on carefully designed experiments and studies that test and retest hypotheses. Psychology also involves rigorous observation. Basing one’s information on experimentation and observation, rather than on abstract theory, is referred to as an “empirical approach” to gaining knowledge.
Hint: Turn on the subtitles and read along with Hank Green. There is a lot of relatively unfamiliar vocabulary in these videos and he speaks quickly.