Relationship problems belie painful truth

Ask most people to define pain and they will probably tell you that pain is the sensation that accompanies injury. This definition is one that focuses more on the stimulus (injury) than on the sensation itself. In academic debate, those who focus on the stimulus are known as the objectivists. Objectivist theories of pain state that pain is merely the awareness of bodily states: the perception or sensory representation of bodily tissue damage.

There are several problems with the objectivist view of pain. First, it tends to collapse into tautology because it fails to make an adequate distinction between stimulus and response. How does the objectivist know that a stimulus is painful? Because it causes pain, which is basically to argue that pain is caused by pain. Second, and more important, the objectivist view fails to account for the dissociations between injury and pain.

In Feeling Pain and Being in Pain , Nikola Grahek spends considerable time discussing a special case of dissociation known as pain asymbolia. Patients with pain asymbolia can readily detect and report the presence of a noxious stimulus, such as a forceful pinprick or searing heat, but will fail to report that stimulus as troublesome. That is, they readily experience the sensory component of pain - where it is, what type of stimulus it is - but they do not experience the unpleasantness and the nasty, motivating impact of pain. These patients can withstand severe tissue damage without withdrawal or any desire to withdraw. Indeed, they laugh at noxious events because they understand that the stimulus is damaging and recognise, intellectually, that it is a threat to bodily integrity, but they do not feel that threat as pain usually demands. Thus, Grahek argues, the feeling of pain cannot be, as the objectivists claim, the perception or representation of bodily tissue damage because pain asymbolia would then be impossible.

Grahek, however, also uses the case of pain asymbolia to undermine those in academic debate who focus on the sensation of pain, known as the subjectivists. The subjectivist view sees pain in terms of the distinctive phenomenal content or quality - the "what-it-is-likeness" - of pain. Grahek argues that those with pain asymbolia experience "the pure juice or essence of pain experience" or a pure pain qualia, but this pure experience is a blunt, fleshless, lifeless experience that has no power to move the mind or body in any way.

Grahek is correct that pain asymbolia undermines the notion that the sensory component of pain is the irreducible essence of pain subjectivity. Those with pain asymbolia have a sensory "what-it-is-likeness" and yet miss some important pain essence, but that hardly finishes off the subjectivist view of pain. There is more to the subjectivity of pain than detecting the type of stimulus in a particular location. Pain subjectivity also includes the nasty, unpleasant, affective component of pain.

Grahek's hasty dismissal of subjectivism is unfortunate because it leads him to a flawed variant of objectivism: that pain is intelligible only when there is a faithful relationship between pain and injury. Grahek takes this intelligible relationship as evidence for dedicated pain fibres and brain centres that dictate pain experience in most normal circumstances. The point is clever because it most certainly is the case that dissociations of pain and injury are highly confusing and troublesome, but the point is also mischievous because such dissociations are extremely common. In a classic experiment, which Grahek cites, researchers waited in a hospital casualty department and interviewed those who entered with injury. Almost 40 per cent reported no pain at all and another 40 per cent reported rather more pain than might be expected, leaving just 20 per cent experiencing the "right" amount of pain for their injury.

It is precisely the failed marriage of pain and injury that makes it so difficult to boil pain down to the physical action of "pain fibres" in the body and "pain centres" in the brain. But even if pain and injury were more faithfully related, boiling pain down to fibres and brain centres would still fail because it would boil pain away: fibres and brain centres do not feel, only sentient subjective beings feel, which is why a subjectivist view of pain must be right. Tragically, Grahek is no longer with us to defend his position, something that I am sure he would have done with excellent humour and matching insight.

Stuart Derbyshire is a senior lecturer in psychology at Birmingham University.