Animal research is controllable. Scientists can control research variables more tightly in animal experiments than in human clinical research. The control, however, results in an unnatural and sometimes pathological setting for the animals, far from their natural habitat. The resulting stress influences the function of virtually every organ, and this confounds the data. Although controlling variables is desirable, it does not justify the use of poorly conceived animal models.
Animal research is traditional.
Whatever the reasons for this cultural phenomenon, the prestige accorded to animal research has important economic implications. Animal research is readily funded. Funding agencies, reflecting the prestigious and familiar positions of animal research in science, often favour these projects. Academic institutions, dependent on grant money for overhead expenses, often require that researchers secure most or all of their own salaries through grants.