Proceedings of the Annual Meeting of the Cognitive Science Society

Humans make frequent and powerful use of external symbolsto express number exactly, leading some to question whetherexact number concepts are only available through the acqui-sition of symbolic number systems. Although prior work hasaddressed this longstanding debate on the relationship betweenlanguage and thought in innumerate populations and semi-numerate children, it has frequently produced conflicting re-sults, leaving the origin of exact number concepts unclear.Here, we return to this question by replicating methods pre-viously used to assess exact number knowledge in innumer-ate groups, such as the Pirah ̃a, with a large sample of semi-numerate US toddlers. We replicate previous findings fromboth innumerate cultures and developmental studies showingthat numeracy is linked to the concept of exact number. How-ever, we also find evidence that this knowledge is surprisinglyfragile even amongst numerate children, suggesting that nu-meracy alone does not guarantee a full understanding of exact-ness.