Humans have remarkable healing abilities. Our bodies can repair tissue, fight infections, and eliminate toxins. These mechanisms, known as “sickness behaviours”, are essential for survival but come at a high cost as immune responses consume a lot of energy and deplete vital nutrients (1). For example: starving bacteria of iron can lead to anaemia; while vomiting and diarrhoea wastes vital fluids and food.
To manage these costs, humans (and many animals) have developed a cognitive system called the Gubernator Medicatrix, nicknamed the health governor (2). This system performs a cost-benefit analysis of self-healing, considering current dangers and future prospects, and uses environmental cues to decide whether activating health defences is worth the expense (3).
For instance, have you ever found that your cold lasts longer in the winter? This is possibly because your health governor, shaped by evolution, deems it safer to conserve resources during this season (4). Whereas, when your health governor senses longer days and predicts the arrival of spring (and, consequently, greater availability of food), it then allows a stronger immune response.
Enter the placebo effect. The placebo effect is often dismissed as being “all in the mind,” suggesting that people only think they feel better when they don’t. Many believe that placebos are essentially useless, serving merely as psychological tricks, but the reality is quite different. We now know that ‘fake medical treatments’ (placebos), although useless in themselves, could create the illusion of a better prognosis. The expectation of a positive outcome induces the health governor to improve its forecast and activate the body’s healing mechanisms.
So, the next time you dismiss the idea of a placebo or hear about a seemingly ridiculous treatment, like baked beans curing cancer, remember that while the treatment itself may not have any direct healing properties, the belief in it can trigger the brain’s healing potential. Support your friends, family or those in your care by creating an environment where healing can occur, as there is power in the placebo.
1 Humphrey, N., & Skoyles, J. (2012). The evolutionary psychology of healing: a human success story. Current Biology, 22(17), R695-R698.
2 Humphrey, N. (2002). Great expectations: The evolutionary psychology of faith healing and the placebo effect. In Psychology at the Turn of the Millennium, Volume 2 (pp. 241-259). Psychology Press.
3 Noakes, T. D., Peltonen, J. E., & Rusko, H. K. (2001). Evidence that a central governor regulates exercise performance during acute hypoxia and hyperoxia. Journal of Experimental Biology, 204(18), 3225-3234.
4 Bilbo, S. D., Drazen, D. L., Quan, N., He, L., & Nelson, R. J. (2002). Short day lengths attenuate the symptoms of infection in Siberian hamsters. Proceedings of the Royal Society of London. Series B: Biological Sciences, 269(1490), 447-454.