A Meta-analytic Review of the Effectiveness of Spacing and Retrieval Practice for Mathematics Learning.

Spaced retrieval practice harnesses two well-studied phenomena: the spacing effect, where spacing out practice over several sessions leads to a gain in retention compared to massed practice in one session; and the testing effect, where material that is tested is better retained than material that is only studied. This meta-analysis investigates if, and under what circumstances, spaced and retrieval practice can benefit mathematics learning. We found a robust small to medium effect of spaced versus massed practice overall (g = 0.26, 25 studies, 49 effect sizes). Those studies can be split into two subsets based on their experimental design, where material was either taught in isolation (8 studies, 23 effect sizes) or as part of a course (17 studies, 26 effect sizes). We found a larger, yet less robust, effect for the isolated material (g = 0.38) than for material embedded into a course (g = 0.24). Our search also revealed 6 studies, 20 effect sizes, which manipulated testing versus restudy. The weighted mean effect of testing versus restudy was g = 0.22, similar to the overall spacing effect. However the 95% confidence interval crossed zero, suggesting the testing effect is not robust. Overall, our results suggest that spaced practice can improve mathematics learning for material in isolation and within a course. However, the effect may be smaller than in other domains. Additionally, the current literature does not provide conclusive evidence for a consistent effect of retrieval practice for mathematics learning, possibly due to the smaller number of studies available.