Since the early 1970s, scientists have used preference tests (tests that require animals to choose between two or more different options or environments) as a means of answering questions about animal welfare. Preference tests have been used to establish animals' preferences for common housing options such as ambient temperature, illumination and preferred types of bedding and flooring; to improve the effectiveness of devices such as loading ramps and nest boxes; and to clarify how strongly animals avoid various aspects of confinement and methods of restraint.
To use preference research to answer questions about animal welfare, three issues need to be addressed. First, we must ensure that experiments do adequately reflect the animals' preferences. The preferences of an animal are likely to vary with the animal's age and experience, the time of day, environmental conditions, and the animal's on-going behaviour; therefore, preference experiments must be comprehensive enough to identify the relevant sources of variation. Experiments must also avoid confounding preference with familiarity, and avoid spurious results arising from the use of particular testing procedures and response measures. Second, to draw inferences about animal welfare from preference research requires that we establish how strongly an animal prefers a chosen option, avoids an unpref erred one, or is motivated to perform a certain behaviour (nest-building, exploration) that is prevented in some environments. Various methods to assess preference and motivation strength have been proposed. Third, the environments preferred by an animal will often, but not always, promote its welfare in the sense of health and psychological well-being. However, preferences may not correspond to welfare if the choices fall outside the animals' sensory, cognitive and affective capacities, or if animals are required to choose between short- and long-term benefits.
Future priorities for preference testing include more emphasis on identifying the factors underlying animals' preferences, greater integration of preference research with other indicators of animal well-being, more reliance on the natural history of the species as a source of hypotheses about environmental preferences, and greater use of preference research in the design of animal environments.
Fraser, D., and Matthews, L.R. (1997). Preference and motivation testing. In M.C. Appleby & B.O. Hughes (Eds.) Animal Welfare. New York: CAB International, pp. 159-173.