What can developmental disorders tell us about the neurocomputational constraints that shape development? The case of Williams syndrome

Abstract

The uneven cognitive phenotype in the adult outcome of Williams syndrome has led some researchers to make strong claims about the modularity of the brain and the purported genetically determined, innate specification of cognitive modules. Such arguments have particularly been marshalled with respect to language. We challenge this direct generalisation from adult phenotypic outcomes to genetic specification, and consider instead how genetic disorders provide clues to the constraints on plasticity that shape the outcome of development. We specifically examine behavioural studies, brain imaging and computational modelling of language in Williams syndrome, but contend that our theoretical arguments apply equally to other cognitive domains and other developmental disorders. While acknowledging that selective deficits in normal adult patients might justify claims about cognitive modularity, we question whether similar, seemingly selective deficits found in genetic disorders can be used to argue that such cognitive modules are pre-specified in infant brains. Cognitive modules are, in our view, the outcome of development, not its starting point. We note that most work on genetic disorders ignores one vital factor: the actual process of ontogenetic development, and argue that it is vital to view genetic disorders as proceeding under different neurocomputational constraints, not as demonstrations of static modularity.

Translational research on early language development: Current challenges and future directions

“…For instance, Robinson, Mervis, and Robinson (2003) reported that 10-year-olds with Williams syndrome relied on their working memory to a greater extent than grammar-matched typical children during language tasks, even when differences in receptive vocabulary skills were covaried. This finding suggests a deviant pattern of language development (see also Karmiloff-Smith & Thomas, 2003). However, other research has provided evidence for a delayed pattern of language production.…”

“…Results of profile analyses within different populations have been especially helpful in debunking stereotypes about different etiologic groups and have highlighted methodological caveats for future research, including the need for longitudinal research and the continued need to evaluate multiple dimensions of language (e.g., vocabulary/semantics, grammar/syntax, and pragmatics) in diverse groups. This research has also fueled and sparked continuing debates among researchers regarding the age-old philosophical question of the ontogenetic association between language and cognition (e.g., Elman et al, 1996;Karmiloff-Smith & Thomas, 2003;Thelen & Bates, 2003).…”

“…Williams syndrome is a rare genetic disorder (incidence between 1/10,000 and 1/20,000 live births) that is caused by a microdeletion of about 20 genes on chromosome 7q11.23 and associated with a highly unusual neuropsychological profile (Karmiloff-Smith & Thomas, 2003;Mervis, 2003;Morris, 2004). Despite moderate mental retardation (average IQ scores range from 50 to 70), individuals with this disorder have surprisingly complex language skills Singer, Bellugi, Bates, Jones, & Rossen, 1994) and tend to be quite affectively expressive and socially attuned (Reilly, Klima, & Bellugi, 1991).…”

“…Some investigators in early studies of this disorder have claimed that the marked language/cognition dissociations observed in individuals with Williams syndrome provide strong support for a "modularity" hypothesis regarding the relationship between language and cognition in ontogeny. However, recent studies evaluating a greater variety of language and cognitive measures at diverse ages have indicated a more complex relationship (Bates, 2003;Karmiloff-Smith & Thomas, 2003;Mervis, 2003).…”

“…One-time "static" snapshots of language behavior so often described in prior language studies are inadequate to capture the dynamic, transactional process of early language development and may yield misleading results (Karmiloff- Smith & Thomas, 2003).…”