An aspect of motivation that is generally considered to be aversive, and may cause stress. Conceptually, suffering has much in common with pain. The problem of assessing pain or suffering in animals is that it can be done only by analogy with ourselves, and this approach is open to the objection that it involves anthropomorphism.
Do animals have to be conscious to suffer? At the commonsense level, we are inclined to suppose that they do. When we are unconscious we do not suffer pain, or mental anguish, presumably because parts of the brain are deactivated. However, we have no conception of what consciousness in animals might involve, if it exists. Therefore we can draw no conclusions about the relationship between consciousness and suffering (or pain) in animals, except by analogy with ourselves. Some animals, especially mammals, have similar behavioural and physiological reactions to stimuli that would induce pain or suffering in us, and we would normally assume that the presence of such reactions indicates that the animal is in pain. The problem is confounded by the fact that non-mammalian animals, with nervous systems very different from ours, show characteristic behavioural reactions to pain stimuli, but their physiological reactions are somewhat different from ours. In the interests of animal welfare, we can give animals the benefit of the doubt, but we have no way of finding out whether their inner experiences of suffering are similar to ours, or whether they suffer at all. Moreover, the concept of suffering is not really necessary to explain animals' avoidance reactions to stress, or to situations likely to cause pain.
Subjects: Zoology and Animal Sciences.