The historical foundation of learning disabilities: A quantitative synthesis assessing the valilidity of Strauss and Werner's exogenous versus endogenous distinction of mental retardation

Werner on the behavioral differences between exogenous (brain injured) and endogenous (familial-cultural) mental retardation using quantitative methods of research synthesis. The concept of exogenous mental retardation evolved into present-day conceptions of learning disabilities. The findings, however, offer little empirical support for the presumed behavioral differences and reveal considerable overlap among the exogenous and endogenous samples studied by Strauss and Werner. Because the behavioral differences were not of sufficient magnitude for presumptive inference about the consequences of brain damage, it is concluded that much of the foundation of the learning disabilities field has been based on overgeneralized assumptions regarding the nature of brain injury, The great tragedy of science—the slaying of a beautiful hypothesis by an ugly fact, —T. H. Huxley IN AN ANALYSIS of the historical foundations of the field of learning disabilities (LD), Kavale and Fornes