classical conditioning - acquiring the phobia through association. Watson and Rayner created a phobia in a 9 month old baby called Little Albert.They conditioned him into being scared of a white rat by associating the white rat with a loud noise e.g a bang
operant conditioning - maintaining the phobia. Responses from classical conditioning decline over time. Reinforcement increases frequency of a behaviour.In negative reinforcement an individual avoids an unpleasant situation.This results in a desirable outcome so the behaviour is repeated. phobia is maintained.
social learning
it is not part of the two process model but it is a neo-behaviorist explanation as phobias may be acquired through modelling the behavior of others.