Carrasco, L., Colell, M., Calvo, M. et al. 2009. Benefits of training/playing therapy in a group of captive lowland gorillas (Gorilla gorilla gorilla). Animal Welfare 18(1), 9-19.
Adding a few minutes of positive human interaction per animal per week to the management of captive gorillas resulted in improved well-being in several areas: the drop in abnormal behaviours, behaviours directed at the public, inactivity and agonistic behaviours, while affiliative behaviours and individual and social play-related behaviour increased.