Attention, eye movement planning and number development in infancy: a cross-syndrome comparison

Numerous studies in animals, adult patients and typically developing infants have suggested that there are two kinds of independent cognitive systems for processing numbers: one for computing approximate numerosities and the other for calculating exact number. Studies focussing on adult patients and typically developing infants cannot determine whether the two specialised number systems are prespecified in the infant brain nor map the relationship between these systems in infancy and the outcome over developmental time, as both of the systems are present early in infancy in typical development. However, results from atypical populations, such as Williams syndrome and Down syndrome, will be discussed in order to shed further light upon these questions, arguing that cross-syndrome differences in large number processing in infancy are more predictive of later development of numerical abilities than small number processing. In addition, evidence from cross-syndrome differences in attention and eye-movement planning will be discussed in order to provide further insight into how domain-general differences impact on the specific number processing systems.