Behaviour is the expression of one’s thoughts and feelings. Behaviour pattern that are expressed outwardly are called as overt behaviour patterns and those that are internal are called as covert behaviour patterns.
Psychology studies mental behaviour. All activities of human behaviour patterns could be fitted into stimulus – response mechanism. (S-R mechanism).
Stimulus is anything that arouses the organism or any of its parts to activity.
A response is he resultant activity that is aroused by a stimulus.