(click here for a more detailed description of methods and results from the Center)
Our research is focused on the etiology and remediation of reading disabilities. Etiological questions are being addressed by testing identical and fraternal twins as part of an NIH Center for the Study of Learning Disabilities (currently funded 2005-2010). We have also worked on the application of computer technology to support the remediation of word-reading and related language disabilities in the schools.
Earlier research in the Center confirmed that reading-disabled
children tend to have a unique deficit in the phonological decoding
component of word recognition, measured by the oral reading of
nonwords (e.g., tegwop, strale). The deficit in this component
word-reading skill is closely related to deficits in an analytic
language skill called phoneme awareness, defined as the ability to
isolate and manipulate the phonemic segments of speech. Bivariate
genetic analyses have indicated that there is a strong shared genetic
influence on disabled readers' deficits in phonological decoding and
phoneme awareness (Gayan & Olson, 2001). More recent
behavioral-genetic analyses have addressed possible independent
genetic influences on a second component word-reading skill called
orthographic coding. One way this is measured is by having subjects
quickly choose the word from two letter strings that would sound the
same if sounded out (e.g., rain rane). The new analyses show clearly
that there are both shared and independent genetic influences on
phonological and orthographic coding skills. Thus, there may be
important individual differences in disabled readers profiles of
component reading skills and in their genetic etiology. Analyses of
disabled readers’ and their siblings’ DNA have found
linkage evidence for a locus on the short arm of chromosome 6 that
appears to be most strongly associated with deficits in orthographic
coding (Gayan et al., 1999).
Beginning in 2001, a new component of the NIH Center, directed by Janice Keenan at the University of Denver, is focusing on deficits in reading and language comprehension. Keenan is studying the same school-age twins that are tested in Boulder on word-level reading and language skills, so the relative contributions of high-level language skills and word-level reading skills can be understood.
A second new component of the NIH Center is focused on the etiology of individual differences in children before they begin formal schooling. Because individual differences in pre-reading skills and environment may have important influences on later reading development in school, we initiated a large longitudinal study of identical and fraternal twins beginning at age 4, with follow-up assessments at the end of kindergarten, first grade, second grade, and fourth grade. A major focus of the study is the assessment of preschool twins’ learning rate from training for the awareness of abstract phonemes in speech. The study includes international collaborations with parallel studies of identical and fraternal preschool twins directed by Brian Byrne in Australia, and Stefan Samuelsson in Norway.
Although our behavioral-genetic analyses of school-age twins have shown a strong genetic influence on many disabled readers' deficits in component reading and language skills, this should not discourage our best efforts toward the environmental remediation of these deficits. A strong genetic etiology only suggests that some extraordinary environmental intervention may be needed to significantly improve some disabled readers' component reading and language skills. Therefore, we have studied the application of computer technology to support the remediation of word-reading and related language disabilities in the schools (Olson & Wise, 2006; Wise et al., 1999, 2000).
Updated: July 17, 2009