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Letter-Discrimination Errors in Kindergarten through Third Grade: Assessment and Operant Training1

Because of the implication of perceptual factors in reading retardation, a number of remedial perceptual-training programs have been developed. These have received some support in the research literature and have grown rapidly in acceptance and use over the past few years. Recently, however, a considerable number of studies have questioned the effectiveness of perceptual-training programs. Hammill (1972) recently reveiwed the literature on perceptual training: