Development of arithmetic across the lifespan: A registered report.

Arithmetic skills are needed at any age. In everyday life, children to older adults calculate and deal with numbers. The processes underlying arithmetic seem to change with age. From childhood to younger adulthood, children get better in domain-specific numerical skills such as place-value processing. From younger to older adulthood, domain-general cognitive skills such as working memory decline. These skills are needed for complex arithmetic such as addition with carrying and subtraction with borrowing. This study investigates how the domain-specific (number magnitude, place-value processing) and domain-general (working memory, processing speed, inhibition) processes of arithmetic change across the lifespan. Thereby, arithmetic effects (carry and borrow effects), numerical effects (distance and compatibility effects), and cognitive skills were assessed in children, younger and older adolescents, and younger, middle-aged and older adults. The results showed that numerical and arithmetic skills improve from childhood to young adulthood and remain relatively stable throughout adulthood, even though domain-general processes, particularly working memory and processing speed, decline with age. While number magnitude and place-value processing both develop until adulthood, number magnitude processing shows deficits during aging, whereas place-value processing remains intact even in old age. The carry effect shifts from a categorical all-or-none decision (whether or not a carry operation is needed) to a more continuous magnitude process in adulthood, reflecting increasing reliance on domain-specific skills. In contrast, the borrow effect remains largely categorical across all age groups, depending on general cognitive processes. These results provide critical insights into how arithmetic skills change over the lifespan, relying on both domain-specific and domain-general processes. (PsycInfo Database Record (c) 2025 APA, all rights reserved).