2016 Gatlinburg Conference Poster
PS-8
Title: Cross-Sectional Trajectories of Language Development in Youth with Down Syndrome
Authors: Gayle G. Faught, Frances A. Conners, Edward C. Merrill, Leonard Abbeduto
Introduction: Language develops atypically in Down syndrome (DS) from infancy to adulthood. Receptive vocabulary is
consistently found to be commensurate with cognitive level across the lifespan. Productive and receptive syntax are often found
to be below cognitive-level expectations, although it is unclear whether this is true at all levels of ability (Abbeduto, Warren, &
Conners, 2007). The syndrome-specificity of the language profile of DS has not been fully explored. The purpose of this study was
to better understand how language develops relative to nonverbal cognitive ability in DS from school-age years to adolescence.
We compared youth with DS to those with mixed-etiology ID and TD children using Thomas et al.'s (2009) innovative crosssectional developmental trajectory analytical approach.
Methods: This study was part of a larger study investigating cognitive predictors of language impairment in DS. Participants
included 36 youth with DS (M age=15.73, SD=3.05), 23 youth with mixed-etiology ID (M age=15.94, SD=2.45), and 50 TD children
(M age=6.68, SD=2.73) matched for nonverbal MA. MA was measured with the Leiter-R Brief and ranged from 4.5 to 9 years in
each group. Among other measures, groups completed three language measures: PPVT-4 for receptive vocabulary, TROG-2 for
receptive syntax, and a narrative task for productive syntax. To compare groups' performances at onset of ability (MA=4.5) and
over increasing ability (MA=4.5-9), we performed cross-sectional developmental trajectory analyses as described by Thomas et
al. This method adapts the SPSS ANCOVA function, using MA as the covariate. It specifically tests group differences in intercept
and slope, with the former indicated by group main effects and latter indicated by group x MA interactions.
Results: For receptive vocabulary, there was no main effect of group, F(2,102)=2.519, p>.05, η2=.047, and no group x MA
interaction, F(2,102)=.976, p>.05, η2=.019. Thus, groups did not differ at onset or over increasing ability. There was a main effect
of MA, F(1,102)=76.684, p<.001, η2=.429, indicating receptive vocabulary improved with increasing ability in all groups.
For receptive syntax, there was a main effect of group, F(2,103)=10.906, p<.001, η2=.175, but no group x MA interaction,
F(2,103)=1.478, p>.05, η2=.028. Follow-up tests revealed TD outperformed DS and ID at onset of ability. Groups did not differ
over increasing ability. There was a main effect of MA, F(1,103)=54.708, p<.001, η2=.347, indicating receptive syntax improved
with increasing ability in all groups.
For productive syntax, there was no main effect of group, F(2,96)=.539, p>.05, η2=.011, and no group x MA interaction,
F(2,96)=.267, p>.05, η2=.006. Thus, groups did not differ at onset of ability or over increasing ability. There was a main effect of
MA, F(1,96)=14.657, p<.001, η2=.132, indicating productive syntax improved with increasing ability in all groups.
Discussion: Overall, language improved with increasing nonverbal ability at a similar pace in DS, ID, and TD. Further, receptive
vocabulary was commensurate with cognitive level at onset and remained so with increasing ability. The same was true for
productive syntax, which has been found to improve in DS, though at a strikingly slow pace. However, receptive syntax was
poorer than cognitive level at onset of ability and remained so with increasing ability in both DS and ID. Poor receptive syntax can
compromise comprehension despite relatively strong receptive vocabulary in DS; thus, language intervention should specifically
aim to improve this domain in DS.
References/Citations:
• Abbeduto, L., Warren, S., & Conners, F. (2007). Language development in Down syndrome: From the prelinguistic period
to the acquisition of literacy. Mental Retardation and Developmental Disabilities Research Reviews, 13(3), 247-261.
• Thomas, M., Annaz, D., Ansari, D., Scerif, G., Jarrold, C., & Karmiloff-Smith, A. (2009). Using developmental trajectories
to understand developmental disorders. Journal of Speech, Language, and Hearing Research, 52(2), 336-358.