The 2019 coronavirus disease pandemic and distrust for popular media have highlighted the need for effective methods of direct communication of biomedical science to the public. It is presently unclear how well nonexperts can learn from primary scientific sources and what factors predict such learning in the general public. The present study examined three modalities for learning about biomedical science directly from study investigators: primary scientific articles, annotated primary scientific articles presented online with interactive learning features, and TEDTalks about scientific studies presented by a study investigator. Each modality presented the same study, "Sleep Drives Metabolite Clearance from the Adult Brain" (L. Xie, H. Kang, Q. Chen, Y. Liao, et al., Science 342:373--377, 2013, https://doi.org/10.1126/science.1241224). Knowledge about the study's scientific content was assessed before and after the randomly assigned learning modality using multiple-choice questions. Participants included a sample of college psychology students and a sample of community-dwelling older adults. Cognitive tests were used to assess individual differences in working memory, processing speed, science literacy, and semantic knowledge. Surveys were used to assess trust in science and scientists, attitudes toward science, and attitudes toward cognitive tasks. Results indicated that both younger and older adults can learn basic biomedical science from a primary source. Knowledge gains were observed in all three learning modalities with no evidence of age group differences. Notably, the largest learning gains for undergraduates and older adults were observed in the primary scientific article condition, followed by the TEDTalk, and the annotated paper. Baseline knowledge about the science study topic and adoption of "scientific attitudes" (e.g., open-mindedness) predicted learning across age groups and learning modalities. These findings suggest that science educators, communicators, and outreach professionals should consider methods of promoting science literacy in the general public through direct access to primary scientific sources.