ABSTRACT
In chapter 4, when the Dodo bird declared, with regard to psychotherapy, that "All must have prizes," the evidence that specific ingredients were not crucial components of psychological treatments began to accumulate. In chapter 5, the search for the efficacy of particular specific ingredients revealed little evidence that anyone ingredient was necessary to produce therapeutic results. Examination of the efficacy of placebo treatments, which contain some but not all common factors, revealed that common factors are indeed related to outcome. Thus far, the evidence seems to indicate that specific ingredients account for little of the variance in outcomes, whereas common factors appear to account for at least a modest amount of variance. If this is the case, then there should be one or more common factors that can consistently be shown to be necessary to produce beneficial outcomes. In this chapter, the size of the general effects produced by the therapeutic alliance will be estimated. If the general effects for this one common factor are relatively large, particularly in comparison with specific effects, then evidence is found to support the contextual model of psychotherapy rather than the medical model of psychotherapy.
