2016 Gatlinburg Conference Poster
PS-59
Title: Language and Phonological Memory Development Over Two Years in Down Syndrome
Authors: Andrew S. Tungate, Frances A. Conners, Leonard Abbeduto, Edward C. Merrill, Gayle G. Faught
Introduction: Down syndrome (DS) results from trisomy of chromosome 21 and is recognized as having a unique developmental
profile, which differs from typically developing children. In particular, syntax and phonological memory are specific challenges,
whereas receptive vocabulary is consistent with nonverbal cognitive ability level. However, there is a need for research on the
developmental course of these abilities in DS. Laws and Gunn (2004) conducted a five-year longitudinal study in DS finding
overall improvements in receptive vocabulary. Interestingly, they found improvements in phonological memory for younger
participants but a decline in performance for older participants. In the present study, we examined individual differences and
change over two years in youth with DS.
Methods: The study included 38 participants with DS, age 10-21 (M= 15.1 SD= 3.3, 47% male) who completed a series of
cognitive tests as part of a larger grant-funded study. All were screened for hearing, vision, and autism. Participants completed
the series of cognitive tests on two occasions separated by two years. Specifically, they completed the Leiter-R Brief as a measure
of nonverbal cognitive ability, PPVT-4 for receptive vocabulary, TROG-2 for receptive syntax, a narrative syntax task, the CELF-P-2
WS Word Structure subtest for productive syntax, the CTOPP Memory for Digits (MD), and Nonword Repetition (NR) subtests for
phonological memory. Growth scale values (GSVs) and raw scores were used in data analyses because of their utility in
measuring performance over time.
Results: There were strong correlations between the two time points across all measures: Leiter-R, r(36)=.88, p<.001; PPVT-4,
r(36)=.90, p<.001; TROG-2, r(36)=.91, p<.001; narrative syntax, r(29)=.85, p<.001; CELF-P-2 WS, r(34)=.94, p<.001; CTOPP MD,
r(35)=.81, p<.001; and CTOPP NR, r(36)=.63, p<.001. There was significant change over two years for only two measures:
improvement in PPVT-4, t(37)=3.02, p<.01, and decline in CTOPP NR, t(37)=3.37, p<.01. However, the pattern of change over two
years was different for younger vs. older participants. The younger subgroup (<15.5 years) improved on Leiter-R, t(18)=2.23,
p<.05, PPVT-4, t(18)=3.47, p<.01, and CTOPP MD, t(17)=2.41, p<.05. The older subgroup (>15.5 years) declined on CTOPP NR,
t(18)=4.18, p<.01.
Discussion: These findings suggest that individual differences in nonverbal cognitive ability, receptive vocabulary, receptive
syntax, productive syntax, and phonological memory are highly stable over a two-year period in DS, when measured by the tests
we used. They also suggest that growth in syntax abilities may slow substantially by middle childhood, whereas nonverbal
cognitive ability, receptive vocabulary, and phonological memory (as measured by digit memory) continue to improve through
mid-adolescence. However, in late adolescence, phonological memory (as measured by nonword repetition) shows marked
decline. These findings are similar to the results reported by Laws and Gunn (2004) and justify further study of the patterns of
growth and decline in language and phonological memory skills in youth with DS. Future studies with larger samples could detect
smaller degrees of growth and decline. Also, further examinations of the intriguing findings related to phonological memory are
warranted.
References/Citations:
• Laws, G., & Gunn, D. (2004). Phonological memory as a predictor of language comprehension in Down syndrome: A fiveyear follow-up study. Journal of Child Psychology and Psychiatry and Allied Disciplines, 45(2), 326-337.
doi:10.1111/j.1469-7610.2004.00224.x