A multilevel meta-analysis on the causal effect of approximate number system training on symbolic math performance.

We performed a meta-analysis of approximate number system (ANS) training studies to investigate the strength of the causal effects of practicing ANS related tasks on symbolic math performance. Across 33 effect sizes from 11 studies involving 754 participants, for which neither the treatment nor control group received symbolic training, we found a small nonsignificant and sensitive effect of ANS training on symbolic math task performance ( = .11, 95% confidence interval, CI [-.