The predictive relationships between working memory skills within the spatial and verbal domains and mathematical performance of Grade 2 South African learners

•The study explored the predictive relationships between WM skills in two different domains (spatial and verbal) and mathematical performance of Grade two learners in South Africa.•A small, but significant association between visuo-spatial WM and mathematical proficiency in a sample of 80 learners, aged 7–8 years was found.•This study provided support that verbal WM was not a significant predictor of mathematical performance in children aged 7 years.•Evidence suggests that in the solving of mathematical problems, the Grade two learners were still reliant on the use of mental models and visual-spatial WM.•Assessing young learners for impaired visuo-spatial skills may help to pinpoint those at risk of developing mathematical difficulties.