what’s the science behind the placebo effect?
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[disclaimer: Not a neuroscientist, just an interested layman] One of the major theories to explain the placebo effect and many other observations is something called “predictive coding” or “predictive processing” [0]. The basic idea is something like this: Your brain receives perceptions from your senses, combined with a confidence level, and it then compares them with its predictions for what it expects to perceive (also with confidence levels). Now, if predictions and perceptions disagree, there are several options:
If the prediction has a low confidence and the perception a high one, the prediction is simply discarded and the brain just considers the the perception [1]. (Imagine you’re sitting in a cafe, your brain predicts (with low confidence) that there will be no movement visible in the corner of your eye, but if someone walks by, you take notice of it)
If the prediction has a high confidence and the perception a low one, then your brain goes with the prediction and discards the perception (you probably didn’t notice me using “the the” earlier, did you?) And lastly, if both conflict and have a high confidence, this triggers “surprisal”
This applies very well to the placebo effect: You have some noisy perceptions of pain, but your brain predicts that the pain should get better, because it has taken “medicine” and so the perceptions get overruled.
[0]: [https://www.cell.com/neuron/fulltext/S0896-6273(14)00192-5](https://www.cell.com/neuron/fulltext/S0896-6273(14)00192-5)
[1]: Technically, the part with lower confidence is not discarded, but both are combined in a way where the part with the higher confidence dominates the end result.
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