Is an objective brain measure of pain possible?

This post is the third in a series of posts on BiM about chapters in the edited collection, Meanings of Pain (2016, Springer).

On the surface, the pursuit of an objective measure of pain seems entirely sensible. After all, if I go and see my doctor and complain of feeling feverish he or she will inevitably take my temperature to obtain an objective measure of my fever. A doctor is unlikely to forgo the thermometer in preference for a 0-10 scale that the patient uses to express how feverish they feel (0 – no fever; 10 – intense fever). By analogy, it appears preferable that medicine dispenses with subjective pain scales (0 – no pain; 10 – intense pain) in preference for brain scans that provide an objective measure of pain.

Obtaining an objective measure of pain with brain imaging faces some practical problems, including the problem that researchers still cannot adequately agree what constitutes the objective pain brain response. Measuring brain activity with an fMRI scanner is not as straight forward as measuring body temperature with a thermometer. But the barriers to using brain scanning as an objective measure of pain are not just practical; in my chapter I argue that it is wrong in principle to believe that brain scans can replace subjective measures of pain.

Examining the analogy with the thermometer in more detail reveals a devastating limitation. Imagine the thermometer fails to provide evidence of an abnormally high body temperature. It might then be reasonable to reject that the patient has a fever, but it would not be reasonable to reject that the patient feels feverish. Now imagine that a patient enters complaining of back pain, but the fMRI scanner reveals no pain brain response. It might then be reasonable to reject that the patient has a pain brain response, but it would not be reasonable to reject that the patient feels pain.

Feeling feverish and feeling pain are fundamentally subjective states. The use of technical devices, such as thermometers and brain scanners, cannot magically transform those subjective states into objective states. That is why efforts to render pain objective with brain scanning creates considerable confusion, and even some lunacy, which I explore in my chapter.

About Stuart Derbyshire

Stuart’s research is mainly concerned with the nature of pain, especially pain that occurs in the absence of identifiable pathology. Consequently, his research abuts psychology, cognitive science, and philosophical ethics. He is currently an Associate Professor in the Psychology Department, National University of Singapore with a joint appointment in the Clinical Imaging Research Centre.

Reference

Derbyshire S. Pain and the dangers of objectivity. In: van Rysewyk S (2016) Meanings of Pain. Springer International Publishing.