Reflection and Experimental Rigor Are Our AiMS: A New Metacognitive Framework for Experimental Design.

Experimental design is a core competency of scientific training with profound implications for research rigor and reproducibility. Yet, trainees often receive minimal guidance to structure their thinking around experimental design. Metacognition-reflecting on one's own thinking-offers a powerful tool to strengthen reasoning in this process. Here, we present the AiMS framework, which adapts the classic plan-monitor-evaluate cycle of metacognition to the context of experimental design. This framework emphasizes three iterative stages-Awareness, Analysis, and Adaptation-that scaffold reflection on an experimental system defined by its Models, Methods, and Measurements and evaluated through Specificity, Sensitivity, and Stability. We illustrate application of the AiMS framework through an interactive neuroanatomy case study and provide a structured worksheet to guide readers in applying it to their own experiments. We also highlight how the framework can assist researchers in organizing their ideas for research proposals and explore the responsible use of generative AI as a metacognitive partner that supports structured reflection without supplanting original intellectual contributions. The AiMS framework complements other principles and practices of rigor by foregrounding deliberate reasoning about assumptions, vulnerabilities, and trade-offs. Our goal is to provide practical tools that foster rigor, creativity, and adaptability in the design of biological experiments, supporting both trainees and their mentors in cultivating reflective scientific practices.