Bidirectional relation of non-symbolic and symbolic numerical systems in first year of kindergarten: the mediating role of ordinality during number learning

Relationship between the Approximate Number System (ANS, an early cognitive system to process non-symbolic magnitudes roughly) and the Symbolic Number System (SNS, a cognitive system to represent exact magnitudes) is a current topic of debate in developmental cognitive psychology. Traditional account states that ANS underlies learning of numerical symbols, while recent evidence argued that SNS develops independently from ANS and, in fact, serves to refine it during mapping. This research studied the direction of this relation and the underlying cognitive mechanisms that mediate it. 180 children were followed during first year of kindergarten. Symbolic and non-symbolic comparison tasks were administered at the beginning (T1) and at the end (T2) of the year, while a cardinality task was administered at T1 and an ordinality task at T2. Results from multiple regression models showed a bidirectional relationship between them. Importantly, ordinality mediated the relationship between SNS at T1 and ANS at T2. This is the first evidence that knowledge of the relationship between numbers, addressed by their ordinal structure, is a key cognitive mechanism that underlies the refinement of the ANS. It supports the notion that both systems develop independently, although they may impact each other at early stages of learning.