Ampofo, DavidApproximate Arithmetic is a task that requires one to approximate the number of dots in dot arrays to add or subtract pairs of dot arrays. Past work has shown that Approximate Arithmetic is a significant predictor of symbolic mental arithmetic. Approximate Arithmetic is thought to engage processes like Visuospatial Working Memory. Those with higher Visuospatial Working Memory ability are better at Approximate Arithmetic. However, few studies have looked at both Visuospatial Working Memory and Approximate Arithmetic’s contribution to variance in mental arithmetic performance. The current study examines the relation between Approximate Arithmetic, symbolic mental arithmetic, and Visuospatial Working Memory. Mediation analyses indicate that the relation between Approximate Arithmetic and mental arithmetic is fully mediated by individual differences in Visuospatial Working Memory. While additional analyses confirm the robustness and dominance of this full mediation model in predicting math ability.enThesisCognitive psychologyApproximate Number systemMathMental arithmeticModular arithmeticOrdinalWorking memory