One of the major challenges of a knowledge society is that students as well as other citizens must learn to understand and integrate information from multiple textual sources. Still, task and reader characteristics that may facilitate or constrain such intertextual processes are not well understood by researchers. In this study, we compare the effects of summary and argument essay tasks when undergraduates read seven different texts on a particular scientific topic, finding that an instruction to write summaries may lead to better understanding and integration than an instruction to write argument essays. We discuss several possible explanations for this result. We also found that beliefs about the certainty of knowledge in some instances can moderate the effect of task on comprehension performance. (Contains 7 tables and 1 figure.)