Experimental Studies of Language Learning Impairment: From Research to Remediation

In the final paragraph of her recent book Uncommon Understanding, Bishop (1997), concludes her comprehensive review of the research literature on etiology, assessment and treatment of children with receptive language impairments with the following quote: "The ultimate test of a hypothesis is through experimental manipulation. If one believes one has identified the primary process that is implicated in SLI, then by ameliorating that deficit, one should be able to show beneficial effects on other aspects of language development. Although applications to intervention are frequently cited by researchers as justification for doing experimental studies, all too often the link with clinical practice is never made. It is time for researchers to recognize that intervention studies are not just an optional, applied adjunct to experimental work, but that they provide the best method available for evaluating hypotheses and unconfounding correlated factors. Intervention studies, such as the methods for sharpening discrimination of rapid auditory stimuli, experimental vocabulary training work, and morphological learning studies, are still very new, but they generate excitement precisely because they allow us to test causal theories directly, and to monitor the process of comprehension development as it occurs". Bishop points out here that not only is it an important aim of research on developmental language disabilities to have this research lead to better assessment and remediation services for affected children, but conversely, remediation research may be one of the strongest means of testing competing research hypotheses. One example mentioned by Bishop, of intervention research that is generating excitement, is the use of acoustically modified speech, coupled with adapted neuroplasticity training, to ameliorate language-based learning disabilities. This research was first published in two papers in Science (Tallal et al, 1996; Merzenich et al, 1996) with additional field trial studies published in a series of subsequent papers (Tallal, 1998; Tallal et al, 1998; Miller et al, 1999; Merzenich et al, 1999; Tallal et al, In Press; Merzenich et al, In Press). These remediation studies grew out of over 25 years of basic and clinical research in two distinct disciplines. One utilized primarily behavioral methods to study the etiology of developmental language-based learning disabilities. The other utilized primarily physiological methods to study neuroplasticity, that is, physiological changes in the brain driven by behavioral training techniques. These remediation studies, conducted both in the laboratory as well as in clinics and classrooms across the USA and Canada have led to the development of a new generation of training programs, the first of which is called Fast ForWord(R). The focus of this paper will be to review the scientific studies that led to the development of these new remediation techniques, based on neuroplasticity research, as well as the outcome data derived from controlled laboratory studies and field trials aimed at assessing the efficacy of these new training methods.