A major cause of poor replicability in animal research is the exclusion of biological variation in study samples through standardization of both genotype and environment, which may produce spurious results. I call for a paradigm shift in study design to improve the replicability of animal research, while at the same time reducing animal use. Specifically, I propose to diversify study populations and include biological variation through deliberate heterogenization of genotype and/or environment as a principle of good study design.

Hanno Würbel's line of research focuses on environment-dependent plasticity of brain and behavior, with regards to the welfare of captive animals and the scientific validity of animal research. He has obtained multiple awards for his 3R research. Besides teaching and research, Hanno has actively engaged in various committees to promote ethically responsible and scientifically valid research.