Adults’ use of subtraction by addition and its association with executive functions

Supplementary materials to: Van Der Auwera, S., De Smedt, B., Torbeyns, J., & Verschaffel, L. (2022). Adults’ use of subtraction by addition and its association with executive functions. Journal of Numerical Cognition, 8(3). 351–366, https://doi.org/10.5964/jnc.7271

This study examined adults’ frequent, efficient and adaptive use of direct subtraction (DS) and subtraction by addition (SBA) in mental multi-digit subtraction with the choice/no-choice method. Participants were offered subtractions in one choice condition (choice between DS and SBA) and two no-choice conditions (mandatory use of either DS or SBA). SBA was used as frequently as DS in the choice condition. DS was most accurate on subtractions with a large difference (e.g., 502 – 18), while SBA was fastest on subtractions with a small difference (e.g., 903 – 886). In general, participants were adaptive for task characteristics and their personal speed characteristics. We further analyzed task-based adaptivity on an individual level via a Latent Class Analysis. Results showed that two-thirds of the participants were adaptive to task characteristics, and that these adaptive participants were the most proficient in accuracy and speed in the choice condition. We further examined whether executive functions (updating, inhibition, shifting) were related to individual differences in strategy efficiency and task-based adaptivity. In line with our hypothesis, updating was related to strategy efficiency, such that participants with higher updating skills were more accurate. In contrast to our expectations, inhibition and shifting were not related to task-based strategy adaptivity. This study highlights adults’ efficient and adaptive use of arithmetic strategies, and its association with their proficiency and executive functions.