Stubbing your big toe on a chair isn’t an incredibly forceful action, but it can certainly hurt like hell. But why does stubbing your toe sometimes feel disproportional in terms how how much pain can be caused by one little action? A recent study decided to take a closer look at why stubbing your toe can be so painful.
Why Unexpected Pain Hits Different
Researchers out of Japan wanted to take a closer look at a phenomenon they call “Bayesian surprise” in terms of pain perception. The concept refers to how our brains process pain when the reality of the situation doesn’t match our expectations. Pain varies from person to person and even within the same person, as sometimes an injury hurts significantly, while other times it is much less intense. Researchers believe part of this difference in pain experience within the individual is tied to an individual’s perception and expectations of pain.
This phenomenon isn’t exactly new, as there have been countless studies on the placebo effect and how our brains work when they believe they are being medicated for a condition. Similarly, the “Bayesian surprise” seeks to explain how our expectations of pain can impact our actual experience.
For the study, researchers had participants wear a virtual reality headset and manipulate a virtual knife with their left hand. Participants were directed to stab the virtual knife into their right forearm when they heard an audible beep. Meanwhile, a thermal device applied real heat to the corresponding spot on their actual arm.
Researchers first tracked how pain experiences changes by varying the timing of the heat simulation. Sometimes the heat was applied as soon as the virtual knife made contact, while other times it was slightly delayed. Occasionally, the knife would disappear in the virtual world right before contact was made with the arm. Researchers tracked brain processes to see how these actions led to different responses within the brain.
Participants reported much higher pain intensity when the heat simulations were delayed and when the knife would unexpectedly disappear. Essentially, patients reported more pain when it came as a surprise. This suggests that our brains perceive pain not just based on the physical stimulus itself, but also by how much that stimulus violates our expectations of pain. When a painful stimulus surprises us, like getting a paper cut or stubbing your toe, the surprise factor may amplify our pain experience.
On a larger scale, this study also suggests why it is so important that doctors work to help their patients have realistic pain expectations during the course of their care. We never want you to be afraid of pain or discomfort that you might experience, but at the same time, if discomfort will be present, we want you to be aware of this. If you underestimate pain or assume painkillers will drown out all your discomfort, you may actually find that your pain levels are amplified because of the surprise factor!
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