Sherwin, C. M. 2004. E2 = 3R + 2Q: Calculating species-appropriate environmental enrichment. Proceedings of the International Congress of the International Society for Applied Ethology, 132 (Abstract).

Species appropriate environmental enrichment should be provided to improve both animal welfare and the quality of research data. For research animals, species-appropriate Environmental Enrichment (E2) can be considered as a function of the 3 Rs (3R) and the Quantity and Quality (2Q) of space that we provide, i.e. E2=3R+2Q. This paper reviews examples of species-appropriate environmental enrichment considering species as diverse as spiders, mice, cattle and primates.