Based on the International Association for the Study of Pain definition
(Iggo 1984), Kavaliers (1989) suggested that for non-humans, pain is ‘an aversive sensory experience
caused by actual or potential injury that elicits protective motor and vegetative reactions, results in learned
avoidance and may modify species-specific behaviour,
including social behaviour’. More simply, Smith &
Boyd (1991) considered pain to be the conscious, emotional experience that, in humans, involves nerve pathways in the cerebrum.