Excerpt:
Subliminal Messages Influence Our Experience of Pain
The brain can learn to associate certain images with more or less pain, even if the images never reach our awareness
By Simon Makin | Aug 13, 2015
Most people associate the term “subliminal conditioning” with dystopian sci-fi tales, but a recent study has used the technique to alter responses to pain. The findings suggest that information that does not register consciously teaches our brain more than scientists previously suspected. The results also offer a novel way to think about the placebo effect.
Our perception of pain can depend on expectations, which explains placebo pain relief—and placebo's evil twin, the nocebo effect (if we think something will really hurt, it can hurt more than it should). Researchers have studied these expectation effects using conditioning techniques: they train people to associate specific stimuli, such as certain images, with different levels of pain. The subjects' perception of pain can then be reduced or increased by seeing the images during something painful.
Most researchers assumed these pain-modifying effects required conscious expectations, but the new study, from a team at Harvard Medical School and the Karolinska Institute in Stockholm, led by Karin Jensen, shows that even subliminal input can modify pain—a more cognitively complex process than most that have previously been discovered to be susceptible to subliminal effects