Learning from expository science texts is challenging. These studies explore whether difficulties can be attributed to poor memory or poor reasoning. To eliminate the need for memory during testing, some students took the tests with the texts available. To test for the effects of reasoning on performance, some students were prompted to engage in explanation activities during or after reading. The effects of these manipulations were tested on text-based and inference questions. Allowing the reader access to the texts during testing improved performance for text-based questions. In contrast, engaging in explanation activities during reading improved performance on inference questions. These results suggest that achieving a better understanding from expository texts depends on engaging in constructive reasoning processes, and not simply improving memory for the texts.