Abstract

Number symbols allow learners to communicate and operate on quantitative information. For more than 50 years, research in mathematics education, cognitive psychology, and neuroscience has investigated the mechanisms underlying the understanding and processing of numerical magnitude, an essential property of numbers. From single-digit and multidigit natural numbers to rational numbers and beyond, learning numerical magnitude presents learners with challenges of increasing complexity across the schooling process. Here, we review interdisciplinary research that has contributed to understanding how people's minds and brains process numerical magnitude through diverse number systems. We focus on main issues during the development of this research, which has mostly relied on number comparison tasks, but it has also incorporated quantity estimation and number line positioning. We include key themes across number systems, such as the emergence of number-space associations and whether perceiving a numerical symbol automatically activates its numerical magnitude.