Developmental versus difference approaches to mental retardation: a theoretical extension to the present debate

The developmental approach to mental retardation is based on the view that comparisons between individuals with mental retardation and individuals without mental retardation matched on cognitive level should indicate no substantive differences in cognitive functioning. In contrast, the difference approach states that such comparisons will often reveal major deficits in cognitive functioning related to IQ. I argued that aspects of the conceptual and methodological foundations of these theories are deficient. An analysis of the relationship between cognitive functioning and cognitive level within designated CA cohorts allows for more sensitive tests of the major propositions in these theories. A paradigm shift based on regression analysis was recommended as the starting point for further theoretical and methodological work in the area.