Behaviourism focuses on external events as the cause of changes in observable behaviours. Students learn behaviours that bring positive feelings and approval from admired people, and change behaviours to satisfy desires they have learned to value. When a teacher constantly reinforces an action, students engage in a routine that enables smooth lessons. Desirable behaviours can be strengthened and undesirable behaviours can be unlearned through reinforcement or punishment. Behaviourist methods like contracts, reinforcement, extinction, and punishment can be used to promote desired classroom behaviours.