Some opponents of the use of animals in research have suggested that captivity alone causes suffering for animals. They argue that distress is indicated whenever an animal shows behavior that deviates from the behavior exhibited by wild conspecifics. This concept of suffering is based on unfounded assumptions about the relationship between behavior of wild and captive animals. Behavior of wild and captive or domestic members of the same species may differ for a number of reasons. For example, many species commonly used in research have been subject to many years (in some cases, thousands of years) of artificial selection by humans. The genetics and the normal behavior of these animals may now be very different from those of their wild progenitors. In addition, many ethological studies, such as the pioneering work of Konrad Lorenz, have shown the importance of early experience on later behavior. Animals of wild parentage, which are born and raised under captive conditions, may behave differently than wild born and raised con-specifics. Such genetic and environmentally determined behavioral differences do not automatically indicate suffering.

Is it legitimate to interpret all behavioral differences between wild and captive animals as negative ones? Animals in captivity are free from the need to watch for and to escape from predators. It is difficult to interpret this alteration in the animal's environment as a negative one, or to conclude that animals suffer by not having to avoid predators (cf. Hediger, 1968). It has been argued that safety alone does not constitute psychological well being, especially for normally social animals housed alone. This is an important consideration, and in this case, knowledge of the behavior of wild animals may be useful in designing research environments which promote psychological well-being.

It is often assumed that wild animals live in a kind of natural paradise and that it is only the appearance and intervention of human agencies that bring about suffering. This essentially Rousseauian view is at odds with the wealth of information derived from field studies of animal populations. Scarcity of food and water, predation, disease and intraspecific aggression are some of the factors which have been identified as  normal parts of a wild environment which cause suffering in wild animals on a regular basis.