To most people, the story of the placebo effect is simple: Because we believe that medicine makes us healthier, a pill—even if it is just sugar—causes us to feel better when we take it. As a result, the placebo effect has generally been considered a conscious process, the result of seeing the pill and the doctor in the white coat who gives it to us.
But a new study, published this week in the Proceedings of the National Academy of Sciences, suggests that the placebo effect doesn’t require conscious perception at all. Instead, we may constantly be registering subconscious cues that directly impact the likelihood of a treatment working.
The researchers at Massachusetts General Hospital who performed the study didn’t give their subjects pills. Instead, they put them through an experiment in which the subjects saw one human face while they were exposed to a very hot stimulus, and another human face while they were exposed to a cooler stimulus. They then showed the subjects each face while exposing them to the same stimulus of medium heat. In this case, the faces were taking the place of the placebo pill, and the heat of the stimulus was taking the place of the physical response to that pill.