Psychology as a Discipline

Long before it became an experimental science, psychology was described, going by its Greek roots (psyche, 'soul', and logos, 'study of'), as the study of the soul or mind. Modern psychology has moved well past that narrow starting point and is now formally understood as the science that studies mental processes, experience, and behaviour in different contexts -- using methods borrowed from both the biological and the social sciences to gather data systematically and turn it into organised knowledge.

The three terms in that definition each name something distinct. Mental processes are internal states of consciousness or awareness -- what is at work when a person thinks, solves a problem, remembers, or perceives something. These processes are reflected in, but not identical to, brain activity: a person's brain can be observed via imaging techniques while they think, yet the mind itself has no physical location the way the brain does, and continues to be active even in sleep (which is why people can dream, register a knock at the door while asleep, or even learn and remember while asleep). Experience refers to the internal, subjective states a person is directly aware of -- pain, romantic feeling, or the heightened awareness some people describe during meditation or under the effect of drugs -- and can only be known first-hand by the person having it; it is also shaped by both internal state and external circumstance (the same crowded, hot bus ride can feel unbearable on an ordinary day and unremarkable on the way to a picnic with friends). Behaviour, finally, is any response or reaction a person makes, from a reflex blink to a considered decision, ranging from simple to complex and from momentary to long-lasting; behaviour can be overt (outwardly visible to an observer, such as running away from danger) or covert (internal, such as the muscle tension a chess player feels while weighing a difficult move) -- and in either case it is triggered by some stimulus, whether external (something in the environment) or internal (a change happening within the person). …