The promulgator of behaviourism, J. B. Watson developed this model. According to him, environment plays important role for the normality and abnormality of the behaviour of an individual. An individual learns the behaviour pattern by interacting with the environment, by experience and practice and by the reward given for the reactions given by him. Continuous, similar and consistent behaviour pattern formulate habit. The abnormal behaviour is produced when a person learns maladjusted behaviour patterns from the environment. By changing the nature of the learned behaviour patterns, the maladjusted behavior can become well-adjusted and normal behaviour can be developed.
The following two processes explain how an individual learns behaviour patterns from his environment : (i) Classical Conditioning (ii) Operant conditioning
(1) Classical conditioning : Russian physiologist Evan Petrovich Pavlov gave the principle of classical conditioning. This principle puts stress on the association between stimulus and response. We already know about Pavlov's experiment on learning. According to this experiment, the CS acquires the capacity to elicit biologically adaptive response through repeatedparing with the unconditioned stimulus. Classical conditioning has its own importance in the field of abnormal psychology. As many of the physical and emotional responses like anxiety, phobia, sexual arousal, alcoholism or drug dependency are mostly learned by conditioning. For example - one can learn a fear of the darkness if fear producing stimuli such as (frightening dreams) occur regularly during conditions of darkness. But the stimulus which produces phobia or fear and anxiety are not so fearful as described by the person.
The conditioning will be strong, if the unconditioned stimulus (food) and neutral stimulus (bell) are presented in pair in classical conditioning. But after the presentation of neutral stimulus (bell), the presentation of UCS (food) is delayed, then learned conditioning becomes weak or the conditioned response will gradually extinguish which is known as extinction. This method of extinction is used for the abnormal behaviour like fear and anxiety.
Prof. B. F. Skinner is associated with instrumental conditioning. It plays an important role in shaping up the behaviour patterns of children. Reinforcement and schedules of reinforcement are in centre in this conditioning. Usually, an individual tries to get the positive reinforcement and to stay away from the punishment. Reinforcement develops the behavior patterns of an individual. The person behaves according to the type of behaviour which elicits reinforcement and becomes firm. Skinner tried to explain adjusted and maladjusted behaviour by the hypothesis of reinforcement and stimulus discrimination. If a person learns to discriminate between two stimuli, he will be able to adjust with the situation. From the stimulus mpresent, what type of response is to be given to which stimulus and what will be the outcome, the understanding of this situation will help the person to get adjusted with the situation. But the person who lacks this type of understanding becomes the victim of maladjustment and gives birth to the abnormal behaviour in long time. From the two stimuli, if a person is able to recognize the maximum useful stimulus and while responding to it, if he gets failure again and again it will lead to depression.