Based on cognitive load theory, the effect of different levels of instructional detail and expertise in a simulation-based environment on learning about concepts of correlation was investigated. Separate versions of the learning environment were designed for the four experimental conditions which differed only with regard to the levels of written instructional detail. One hundred and forty Grade 10 (lower-expertise) and Grade 11 (higher-expertise) students participated in this experiment. In accord with the expertise reversal effect, the results supported the hypothesis that higher levels of instructional detail benefited learning for lower-expertise learners, whereas lower levels of detail facilitated learning for higher-expertise learners. It was concluded that the level of instructional guidance needed to match learners' levels of expertise.