This study examined the extent to which prior beliefs and reading instructions impacted elements of a reader's mental representation of multiple texts. College students' beliefs about childhood vaccinations were assessed before reading two anti-vaccine and two pro-vaccine texts. Participants in the experimental condition read for the purpose of integrating across the texts, while those in the control condition read for comprehension. Participants completed a vocabulary assessment then post-reading essays, which were scored for the quality of argumentation and organization. Results indicated that those who were instructed to integrate, held accurate beliefs about vaccines, and demonstrated higher vocabulary knowledge tended to write more organized essays. Participants with inaccurate beliefs about vaccines produced essays that were more incoherent and polarized, even when asked to integrate texts. Although prompting readers to integrate might generally contribute to a more organized mental representation, a more robust intervention may be needed when misconceptions are present. [This is the online version of an article published in "Reading Psychology."]