Q.What is behaviour? Give examples of overt and covert behaviour.

Behaviour, in psychology's own working definition, is any response or reaction a person makes, or any activity they engage in -- and it forms one of the three core things (along with mental processes and experience) that the discipline studies. Behaviours can be simple, such as a reflex blink when something is suddenly thrown toward a person's face, or complex, such as deciding which film to watch with a friend after weighing several considerations; they can also be brief and short-lived, or drawn out and enduring over a long stretch of time.

Psychologists find it useful to split behaviour into two broad kinds based on whether an outside observer can directly witness it. Overt behaviour is outwardly visible -- it can be seen or otherwise sensed by someone watching from outside, such as a person's heart visibly pounding with nervousness while writing an exam, or their legs moving as they run from a perceived threat. Covert behaviour, by contrast, is internal and not directly observable by anyone else -- for instance, the way a chess player's hand muscles may tense up while mentally rehearsing a difficult move, without the player necessarily making any visible movement at all; only careful physiological measurement, or the person's own report, can reveal that this covert activity is happening.

Both overt and covert behaviour share one important feature: each is triggered, or set off, by some stimulus -- a triggering event or condition -- which can itself be either external (something happening out in the environment, such as an object flying toward a person) or internal (a change happening within the person, such as a rising level of anxiety before a test). Historically, behaviourist psychologists such as John Watson treated this stimulus-response (S-R) link as the whole of what a scientific psychology should study, precisely because both the external stimulus and the overt response could, at least in principle, be observed and measured objectively, whereas covert, internal behaviour and mental processes could not be verified from outside in the same way. Even so, the modern, broader definition of psychology treats overt and covert behaviour as equally real and equally worth studying -- covert behaviour is simply harder to observe directly, not less genuinely present, and much of what makes psychology distinctive as a science lies precisely in developing careful methods to study exactly this kind of internal, only partly observable activity.