Specificity Theory

The search for a working model, or theory, of how pain works has probably been going on as long as the concept of pain has been in existence. Descriptions of pain treatment were recorded as early as 4000 B.C. in ancient Egypt. Throughout history, several theories of pain have dominated current thinking. With advances in our understanding of biology, psychology, and with the advent of new medical technologies, older theories have been replaced or updated.
Descartes specificity theory


Descartes’ (1664) concept of the pain system was of a ‘straight-through’ channel running from the skin to the brain, which transmits the sensation of pain from one place to another in the way that ‘a rope pulled in one room causes a bell to ring in another’. Specificity theory suggests the existence of a specific pain system which carries messages from pain receptors in the skin to a pain area in the brain. Specificity theory may sound reasonable to those of us who have only experienced pain following tissue damage. However, there are scientific findings that specificity theory cannot account for. For example, the phantom limb pain felt by amputees – if the sensation of pain is generated at the level of the pain receptor and transmitted faithfully to the brain, how can pain exist when the receptors are no longer there and the nerve fibres to the brain are cut? Specificity theory also cannot explain what is happening in patients who feel pain in the absence of any stimulus.


Descartes rationist epistemology


The way which Descartes arrived at his theory was through his own deductive reasoning. Descartes would have known that nerve fibres existed, but his description of how they functioned was based purely on his own thoughts and was not linked to scientific evidence. Although this method sounds unusual to us in the present day – where hypotheses must be rigorously tested – during Descartes’ time it would have been quite acceptable to arrive at conclusions simply through reasoning. This is typical of the rationalist epistemology popular at that time, where the source of knowledge and truth was believed to be intellectual and deductive, rather than sensory. The modern scientific method is based in empiricist epistemology, which asserts that true knowledge can only be based on experience and evidence. Despite the shift in scientific thinking towards empiricism in the 17th Century, Descartes theory persisted in some form until the mid 19th Century.


Sources:
Descartes, R., & Hall, T. S. (2003). Treatise of Man (Vol. 8). Prometheus Books.
Gatchel, R. J. (1999). Perspective on Pain: A historical Overview. In R. J. Gatchel & D. C. Turk (Eds.), Psychosocial Factors in Pain: Critical Perspectives (pp. 3–17). NY: Guilford Press.





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