What should you measure?
Since Freud's pioneering work in the 19th century, psychotherapy has undergone a process of evolution, and it has long been more accurate to talk of a range of psychological interventions, each employing more or less distinctive techniques. Whereas some have retained the models of unconscious motivation of psychoanalysis, others have eschewed it; some focus on the remoter aspects of the patient's past, whereas others are interested only in present experience and functioning. To a great extent, the tensions created by the emergence of new models and ideas have been helpful and creative, forcing an examination of practice, and leading to the development of further methods of intervention. Equally they have the potential to overemphasize what is distinctive about therapies at the cost of neglecting their commonalities.