"The word ‘pain’ is used in different ways. The most frequent use, especially with respect to subjects that cannot communicate verbally, is in describing the behavioural response to noxious stimulation. However, if we accept this use, we are presented with the difficulty of distinguishing between the responses of simple versus complex organisms. Fruit fly larvae, for example, have been demonstrated to bend and roll away when approached with a naked flame but most people would agree that larvae do not feel pain in the way that we do. Ruling out the responses of larvae and similarly simple organisms as indicating pain is possible if we suggest that responses must include more than mere reflex responses to be labelled as a pain response. When someone reaches out and accidentally touches something very hot, there is an immediate tendency to drop the object. That reaction is entirely regulated by a simple loop of sensory neurons speaking to motor neurons in the spinal cord. Typically, the person will drop the object before there is any conscious appreciation of pain. The action of dropping the object indicates the presence of something noxious but does not necessarily indicate the presence of pain."