Numerical information can be conveyed by either symbolic or nonsymbolic representation.
Chao Liu, Honghong Tang, Yue-Jia Luo, Xiaoqin Mai 2011, 'Multi-Representation of Symbolic and Nonsymbolic Numerical Magnitude in Chinese NumberProcessing', PLoS ONE10.1371/journal.pone.0019373. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Others suggest that symbolic and nonsymbolic magnitudes have distinct and non-overlapping representations.
Anna A. Matejko, Daniel Ansari 2016, 'Trajectories of Symbolic and Nonsymbolic Magnitude Processing in the First Year ofFormal Schooling', PLOS ONE10.1371/journal.pone.0149863. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
However, number-related brain networks seem to be particularly sensitive to nonsymbolic arithmetic training.
Camilo Gouet, César A. Gutiérrez Silva, César A. Gutiérrez Silva, Bruno Guedes, MarcelaPeña 2018, 'Cognitive and Neural Effects of a Brief Nonsymbolic Approximate Arithmetic Trainingin Healthy First Grade Children', Frontiers in Integrative Neurosciencehttps://www.frontiersin.org/article/10.3389/fnint.2018.00028/full. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
In line with previous studies, performance on both symbolic and nonsymbolic magnitude processing was related to math ability.
Gavin R Price, Lynn S Fuchs 2016, 'The Mediating Relation between Symbolic and Nonsymbolic Foundations of Math Competence.',PLoS ONEhttp://europepmc.org/articles/PMC4747497?pdf=render. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)
Different studies found out that nonsymbolic estimation could foster subsequent exact number processing and simple arithmetic.
Sonja Maria Hansen, Hilde Haider, Alexandra Eichler, Claudia Godau, Peter A Frensch,Robert Gaschler 2015, 'Fostering Formal Commutativity Knowledge with Approximate Arithmetic.', PLoS ONEhttp://europepmc.org/articles/PMC4652602?pdf=render. Retrieved from PLOS CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)