Veissier I, Forkman B. The Nature of Animal Welfare Science. ARBS Annu Rev Biomed Sci 2008;10:T15- T26. The societal concern for animal welfare stems from the acknowledgement that they are sentient beings, whether their sentience makes morally unacceptable any act that would increase their suffering (utilitarian point of view) or animals deserve rights because of their sentience (animal rights point of view). Several definitions of animal welfare have been proposed, based on common sense, mechanisms, or operational indicators. These definitions should not be interpreted as uncertainties about the existence of the concept but rather as different aspects of the same concept. Whatever the definition used, research on animal welfare attempts to answer the following questions: To what extent are the animals used by humans capable of emotions? How does an animal perceive its environment? How can we assess the level of animal welfare in a given situation? What are the impacts of the ways we treat animals on their welfare? To answer these questions, animal welfare scientists borrow methodologies and theoretical frameworks from various disciplines, mainly behavioural sciences, including not only ethology but also experimental psychology, animal cognition, or stress physiology. The focus is not on the description of animal behaviour or stress responses but rather on the understanding of how animals experience their world. Hence the recent developments issued from psychology, studying cognitive bias or relations between cognition and emotions. Animal welfare science can be considered as a new behavioural science, applied to societal concerns about our relations to animals, with specific research questions and methodologies inspired by other disciplines.