over time. In this way, initial, genetically conditioned behavioral differences between individuals with different syndromes or between individuals with a syndrome and typically developing individuals will be magnified over time. Moreover, these indirect effects may be seen not only on subsequent language development, but also on developments in other domains of psychological and behavioral functioning because language is so often the system that mediates an individual's interactions with his or her world.
Second, it is important to place behavioral differences between syndromes, such as described in this chapter, in proper perspective. One interpretation of syndrome differences on some dimension(s) of behavior is that such differences are evidence of a need to create new, syndromespecific interventions or educational environments for individuals with a given syndrome. This interpretation, however, does not take into account that there are far more commonalities than differences between most genetic syndromes associated with mental retardation, at least at the level of behavior. Thus, it is probably more appropriate to use data on syndrome differences to customize existing programs, interventions, and strategies rather than creating them anew according to a syndrome-specific profile.
The research reported in this chapter was supported by NIH grant R01 HD24356 awarded to the first author, fellowships awarded to the second author through the John H. Merck Scholars II program and the Jeanette Anderson Hoffman Memorial Wisconsin Distinguished Graduate Fellowship, and NIH grant P30 HD03352 awarded to the Waisman Center. We gratefully acknowledge the contributions of the following colleagues to the research reported in this chapter: Adrienne Amman, Parti Beth, Lori Bruno, Stephanie Cawthon, Ingrid Curcio, Nancy Giles, Patti Johnstone, Selma Karadottir, Susan Kirkpatrick, Doris Kistler, Pamela Lewis, Robert Nellis, Erica Kesin Richmond, Shannon Theis Romanski, Jillyn Roxberg, Susen Schroeder, Susan Vial, Katey Verberkmoes, Elizabeth Wall, and Michelle Weissman. We are indebted to the families who participated in the research so enthusiastically and patiently.
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