Of all the animals used for invasive research, nonhuman primates are perhaps the most controversial. While the total number of animals used in experiments and covered by animal welfare laws has declined in recent years, the number of nonhuman primates used has increased.
Debates over the use of animals for research often center on the animals’ experience of pain. Animal welfare regulations require researchers to report whether the animals they use are subjected to pain and whether it is relieved by medication. If pain is unrelieved, researchers must give a justification.