<p>The ability to integrate information from conflicting sources into an argumentative synthesis is essential in higher education, yet it remains a challenging task for students. While supporting learners during the writing process has shown promise in fostering synthesis skills, limited research has examined how instructional aids influence synthesis processes and their relationship to the final written product. This study examined the impact of two instructional aids (a guide and a rubric) compared to a control condition, focusing on their influence on synthesis processes, text quality, and the contribution of process variables to synthesis outcomes. Fifty-eight undergraduate psychology students were randomly assigned to one of three groups (guide/rubric/control). They participated in three sessions (pretest/intervention/posttest), where they wrote an argumentative synthesis using <i>keystroke logging software</i>. In the intervention session, the guide and rubric groups applied their respective aids, while the control group worked without support. Synthesis writing quality was assessed at the level of integration, while the writing process was examined using Inputlog indicators (recursiveness, transitions between sources, proportion of active writing, writing fluency, product/process ratio, and time on task). Results showed that both aids enhanced integration strategies and increased recursive engagement with reading and writing. The guide was particularly effective in supporting revision, while the rubric influenced textual production. Additionally, source use and writing fluency significantly predicted synthesis quality, regardless of the aid provided. These findings deepen our understanding of how writing processes relate to product quality and offer practical implications for designing effective instructional interventions in academic writing.</p>