Important claims have been made regarding the contrasting profiles of
linguistic and cognitive performance observed in two genetically based
syndromes, Williams syndrome (WS) and Down syndrome (DS). Earlier
studies suggested a double dissociation, with language better preserved
than nonverbal cognition in children and adults with WS, and an
opposite profile in children and adults with DS. More recent studies
show that this initial characterization was too simple, and that
qualitatively different patterns of deficit observed within both
language and visual–spatial cognition, in both groups. In the
present study, large samples of children and adolescents with WS and
age-matched DS are compared with typically developing (TD) controls
matched to WS in mental age, on receptive and expressive lexical and
grammatical abilities, semantic and phonological fluency, digit span
and nonverbal visual–spatial span, and on 2 visual–spatial
construction tasks. Study 1 confirmed distinct profiles of sparing and
impairment for the 2 groups, within as well as between language and
nonlinguistic domains, even after IQ variations were controlled. In
Study 2 we compared performance of the children, adolescents and young
adults with DS and WS included in the first study, divided on the basis
of the chronological age of the participants (under 8 years; over 12
years). Although it is important to stress that these are
cross-sectional rather than longitudinal data, the results demonstrated
that the profile of younger children is different in respect to those
of the older children; initial states of the system cannot be inferred
by the final state. Possible neural substrates for these profiles and
trajectories are discussed. (JINS, 2004, 10,
862–876.)
