Abstract
IntroductionAdults can represent numerical information in nonsymbolic and symbolic formats and flexibly switch between the two. While some studies suggest a strong link between the two number representation systems (e.g., Piazza, Izard, Pinel, Le Bihan, & Dehaene, 2004 Neuron, 44(3), 547), other studies show evidence against the strong‐link hypothesis (e.g., Lyons, Ansari, & Beilock, 2012 Journal of Experimental Psychology: General, 141(4), 635). This inconsistency could arise from the relation between task demands and the closeness of the link between the two number systems.MethodsWe used a passive viewing task and event‐related potentials (ERP) to examine the temporal dynamics of the implicit integration between the nonsymbolic and symbolic systems. We focused on two ERP components over posterior scalp sites that were found to be sensitive to numerical distances and ratio differences in both numerical formats: a negative component that peaks around 170 ms poststimulus (N1) and a positive component that peaks around 200 ms poststimulus (P2p). We examined adults' (n = 55) ERPs when they were passively viewing simultaneously presented dot quantities and Arabic numerals (i.e., nonsymbolic and symbolic numerical information) in the double‐digit range. For each stimulus, the nonsymbolic and symbolic content either matched or mismatched in number. We also asked each participant to estimate dot quantities in a separate behavioral task and observed that they tended to underestimate the actual dot quantities, suggesting a need to adjust the match between nonsymbolic and symbolic information to reflect the perceived quantity of the nonsymbolic information.ResultsUsing this adjustment, participants showed greater N1 and P2p amplitudes when perceived dot quantities matched Arabic numerals than when there was a mismatch. However, no differences were found between the unadjusted match and mismatch conditions.ConclusionOur findings suggest that adults rapidly integrate nonsymbolic and symbolic formats of double‐digit numbers, but evidence of such integration is best observed when the perceived (rather than veridical) dot quantity is considered.
Highlights
Adults can represent numerical information in nonsymbolic and symbolic formats and flexibly switch between the two
Previous research has shown that people have access to two systems representing numerical information: One is an approximate number system (ANS) that represents the numerical magnitudes from nonsymbolic numbers >4; the other is a symbolic number system (SNS) that allows for the representation of exact numerical information provided by symbolic numbers (e.g., Arabic numerals or number words)
The present study tested the integration between nonsymbolic and symbolic numerical formats in the adult brain
Summary
Adults can represent numerical information in nonsymbolic and symbolic formats and flexibly switch between the two. Previous research has shown that people have access to two systems representing numerical information: One is an approximate number system (ANS) that represents the numerical magnitudes from nonsymbolic numbers >4 (e.g., a dot quantity containing 23 dots as “twenty-ish”); the other is a symbolic number system (SNS) that allows for the representation of exact numerical information provided by symbolic numbers (e.g., Arabic numerals or number words). While these two systems differ fundamentally in their representational capacities, there is evidence to suggest that they are integrated. Converging evidence from developmental and comparative studies as well as studies with people whose languages do not have number words shows ratio-dependent performance on nonsymbolic number comparison tasks suggesting a key feature of the ANS: independence from language (Cantlon, Brannon, Carter, & Pelphrey, 2006; Izard, Sann, Spelke, & Streri, 2009; Libertus and Brannon, 2009; Lipton & Spelke, 2003; Nieder, 2009; Pica et al, 2004; Xu & Spelke, 2000)
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