Plain Language in Interactive Systems: A Systematic Mapping of Domains, Practices, and Challenges

Context: Plain Language is a multidisciplinary technique and civic movement that aims to make it easier for users to find, understand, and use information, whether in documents, digital interfaces, or data visualizations. Its adoption has expanded in areas such as Government, Health, and Law, driven by legislation and public policies. In Computing, specifically in the area of Human-Computer Interaction, this technique presents itself as an important quality attribute in systems for inclusion, transparency, and digital accessibility. Objective: This study investigates how Plain Language has been applied in the design of interactive systems in HCI, identifying domains, objectives, methods, challenges, and other aspects reported in the literature. Method: We conducted a systematic mapping study following a rigorous protocol, encompassing data search, filtering, and extraction. We also followed a qualitative approach based on thematic analysis for coding and synthesizing the 18 selected studies. Results: The results reveal a predominance of studies in the health domain and a strong focus on comprehensibility, mainly applied during evaluation stages. Limited use of Plain Language was observed in early design phases and challenges in scalability and limited automation, insufficient user-centered and qualitative evaluations, and limited consideration of cultural factors. Conclusion: The results indicate that Plain Language is still applied in a limited way in HCI, pointing to opportunities for deeper theoretical integration, broader design support, and more robust methods for inclusive and efficient interactive systems.