Moderators & Protective Factors
Rutter has enlightened scholars that the effect of a risk factor on a disorder may vary across contexts, populations, or circumstances. That is, the magnitude of an effect might be reduced (or enhanced) under different conditions. For example, the effect of early harsh discipline on the development of conduct disorder is reduced under circumstances of a warm parent-child relationship. This phenomenon is called a moderator effect and is defined by a significant interaction effect between a risk factor and a moderating factor in the prediction of a disorder.
Moderator variables have also been called protective, or buffering, factors. A protective factor protects, or buffers, the individual from the pathogenic effects of a risk factor. Intelligence and a positive relationship with a caring adult have been the most commonly studied protective factors for a variety of disorders. One remaining question is whether protective factors operate more strongly in high-risk than in low-risk groups; that is, if a variable buffers both low-risk and high-risk groups from risk, it is not clear whether that variable would be defined as a protective factor (or simply another predictor variable).
Intervention & Prevention As Experiments
The relation between the scientific study of behavior in developmental psychology and the application of scientific principles to psychiatry is reciprocal. Concepts from developmental psychology have been applied in psychiatric practice, but psychiatric intervention can also be viewed as a field experiment to test hypotheses about behavioral development. Systematic intervention and prevention can be viewed as experiments to test basic principles. In fact, given the complexity of human behavioral development and the ethical restraints against known iatrogenic manipulations, clinical practice may be the most powerful scientific tool available to test hypotheses from developmental psychology. Thus the relation between these disciplines is reciprocal, and communication between the disciplines must be preserved.