One commonly cited feature of Williams syndrome is a
characteristic dissociation between
relatively spared language skills and severely impaired nonverbal abilities.
However, the
actual evidence for a dissociation between verbal and nonverbal abilities
in Williams
syndrome is equivocal. In two separate studies we examined these abilities
in 16
individuals showing the Williams syndrome phenotype. When considered as
a whole, the
group did have significantly superior verbal abilities, but this
difference was caused by a large
discrepancy in abilities in only a small number of individuals. In both
studies there was a
clear, linear relation between individuals' verbal ability, and the
magnitude of their
verbal–nonverbal discrepancy. We suggest that these results
are best explained in terms of
verbal ability developing at a faster rate than nonverbal ability in this
disorder. We discuss
how this model of differential rates of development has the potential to
reconcile the
apparently inconsistent findings in this area.