Q.Explain what psychologists mean when they say that experiences are 'subjective' in nature.

Psychology's formal definition treats it as the science that studies mental processes, experience, and behaviour in different contexts, and each of these three terms names something genuinely distinct, even though all three are closely interconnected in practice. Mental processes are internal states of consciousness or awareness -- what is happening when a person thinks, tries to solve a problem, or works to know or remember something. One level at which mental processes show up is brain activity, which can be observed in real time using brain-imaging techniques while a person is thinking or solving a problem; but mental processes and brain activity, though interdependent, are not identical, since the mind, unlike the brain, has no physical structure or location and continues showing activity even during sleep.

Experience refers to the subjective, internal states a person is aware of -- pain, or a positive feeling such as romantic attraction -- and its defining feature is that it can only be directly known, first-hand, by the person actually having it; an outside observer cannot directly observe someone else's experience the way they can observe a physical event. Psychologists have studied experiences ranging from the pain of a terminally ill patient or someone in bereavement, to positive experiences such as romantic encounters, to more unusual, esoteric experiences such as the altered state a meditating yogi may enter, or the artificially induced experience sought by someone using a drug. Because experience is shaped by both a person's internal state and their external circumstances at the time, the very same objective situation -- for instance, a hot, crowded bus ride -- can be experienced very differently depending on those surrounding conditions.

Behaviour, finally, is any response, reaction, or activity a person engages in, ranging from a simple reflex to a complex, deliberated decision, and from momentary to long-lasting. Behaviour can be overt (visible to an outside observer) or covert (internal, not directly observable), and in either case it is triggered by some stimulus, whether external or internal. Because mental processes and experience are inherently harder to observe directly than behaviour, much of the historical debate about what makes psychology properly scientific has centred on how to study these two carefully and rigorously, rather than restricting psychology only to what is easily, directly observable.