A study of monkey behavior. Here the behavior of the monkey is monitored as he reacts to a visual stimulation box above his head. He is held in a ventilated metal and plastic primate restraining chair. Animal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals in experiments that seek to control the variables that affect the behavior or biological system under study. Animal rights organizations question the need for and legitimacy of animal testing, arguing that it is cruel and poorly regulated or that animals have the intrinsic right not to be used or harmed in experimentation.