ABSTRACT
This chapter highlights an important difference between adult neuropsychological models and truly developmental approaches to neurodevelopmental disorders, namely that adult models tend to be static and developmental approaches. It explores how genotype to phenotype mapping depends on developmental time. The chapter provides an example of how a developmental explanation is needed to map findings of atypical neural processing for faces and language to relatively proficient face and language processing behaviours in adults with Williams syndrome (WS). It argues that the atypical genetic profile found in neurodevelopmental disorders affects brain development from the start of ontogenesis, impacting low-level, domain-general processes that cascade over developmental time and affect neural specialisation processes in later development. The chapter provides one such example where cross-syndrome differences in number processing by adults with Down syndrome (DS) and WS may be partially explained by differences in basic-level attentional processes in very early development.
