The 1950 and 1960s witnessed a revival of interest among psychologists in mental retardation closely associated with the development of a behaviourist model. These developments effected a decisive break in the discourse of retardation by inserting a 'behaviour' component into the definition of retardation. This strengthened claims by psychology of professional primacy vis-à-vis medicine. The objective of professional assertion helped create the conditions in which the service model of Normalisation 2 took root in North America and, to a lesser extent, the UK. As a semi-autonomous discourse, Normalisation provided a vehicle in which elements of contradictory discourses, principally psychology and interactionism, could be appropriated. The interventions which emerged from this comprised a dual strategy of enhanced social integration and the more precise definition and identification of mental retardation.