Behaviour therapy is based on the principles of learning theory, and assumes that neurotic behaviour consists of learned maladaptive habits. Following the work of Pavlov (1927) with experimental neuroses, and that of Watson (1920) on the elimination of children's fears, Wolpe (1958) devised a method suitable for treating patients with phobias. This involves deconditioning with the aid of reciprocal inhibition. The patient is introduced to a graduated series of the relevant anxiety provoking stimuli, and at the same time the anxiety responses are inhibited by means of relaxation. The latter state may be induced by hypnosis, Jacobson's method (1938), or by drugs.