One psychological explanation for OCD is the behavioural approach. The behavioural approach breaks obsessions and compulsions into separate categories. Mowrer (1960) suggests that the acquisition of fear and anxiety is a two-step process in which firstly the neutral stimulus is associated with anxiety through classical conditioning for example a child being told that food which has been dropped on the floor is disgusting, this then creates anxiety for the child and from this point on when the child thinks of anything dirty, anxiety is created. The second part of the process assumes that the anxiety which has been created is then maintained overtime through avoidance which leads to positive outcomes and therefore is reinforced. The behavioural approach also suggests that compulsive rituals are learned due to a link between the anxiety associated obsession and the reduction of that anxiety. As a result ritualistic behaviour is reinforced and a person may link the act they have performed with changing the fearful situation which causes an accidental association to be formed which has the potential to become compulsive when an individual faces thoughts or situations which provoke anxiety.
Another psychological explanation of OCD is the psychodynamic approach suggested by Freud (1917) which assumes OCD arises when unacceptable wishes and impulses coming from the id are only partially repressed. These partially repressed thoughts then can provoke anxiety within a person. OCD sufferers use ego-defence mechanisms in order to reduce the feeling of anxiety associated with the impulses and wishes. There are three main ego defence mechanisms. Isolation is a defence mechanism where an attempt is made to isolate oneself from undesirable wishes and impulses. The id and defence mechanism fight for predominance and when the id succeeds the impulses intrude as obsessional thoughts. When isolation is