more evidence the mind believes what it wants to believe

In the last post I suggested that when the brain is prepared to expect something, it will imperceptibly adjust its perceptions to "see" what it expects to see.

It will also "feel" what it expects to feel, according to a new study.

We're all familiar with the placebo effect: patients who pop sugar pills, instead of real meds, will often report their symptoms gone (to a greater degree than patients who don't take real meds or a placebo). Now researchers have shown the reverse effect: if you give a patient a drug but don't tell them, they may not perceive any positive effects.

The researchers inflicted some pain (via heat) on a group of willing subjects, who were also tapped into an IV drip. Without any painkillers, the subjects reported experience pain at a level of 66 (out of a maximum of 100). When a strong painkiller was added to the drip - without them knowing - their pain levels dropped to 55, and when told that they had received a strong painkiller they reported feeling pain at a 39. That much is consistent with the "placebo effect" - the knowledge of getting meds can be as, or more, effective in reducing symptoms as the drug itself.

What struck the researchers, though, was what happened when they told subjects that they stopped giving in the painkiller, but in fact continued to drip it in. Subjects said their pain went back up to 64. They might as well have not been receiving any painkillers at all.

Pain is probably one of the most subjective of sensations, so it may not be a surprise that our experience of pain is "all in our head." Nonetheless, if our perception of pain can be entirely determined by our expectations of pain, then what other "perceptions" of ours may be partly, if not wholly, be pre-set by our minds?