"Scientists and doctors have been studying placebos for more than half a century. These inert "sugar pills" remain highly controversial, yet they are widely used in clinical treatment today—especially in the area of pain management. So-called "placebo analgesia" has been observed again and again not only in the pain clinic, but also in the neuroscience lab, where scientists have documented a placebo response in the brain's pain pathways.

Despite this evidence, nobody really understands the psychological processes involved in placebo analgesia. Presumably the power of these inert substances has something to do with the expectation of relief, but how do expectations translate into basic cognitive processes, like attention and thought? One possibility is that when sufferers expect relief, they are able to redirect their attention away from their pain, creating an analgesic effect. If that's the case, then expectation itself might actually act as an agent of cognitive control, and the mind's executive powers might be the link between expectation and relief. Imaging studies have revealed placebo-related activity in a brain region involved in executive function—bolstering this theory.

But this brain imaging evidence is merely suggestive, and the theory has never been tested directly. A team of psychological scientists, headed up by Jason Buhle of Columbia University, decided to investigate this explanation for placebo analgesia. The brain has a limited supply of cognitive power, so if indeed placebo analgesia requires executive attention, then performance on a demanding cognitive task should interfere with pain relief from a placebo, and vice versa. One kind of executive power is working memory, and in previous work Buhle and colleagues have shown that performing a difficult working memory task itself reduces pain, presumably by distracting sufferers. So in a new experiment, they tested whether this same cognitive task interferes with the relief offered by a placebo drug, as one would expect if they are using the same cognitive mechanisms. If not, then the evidence would suggest that sugar pills and distraction have independent analgesic effects."

Read more at Psychological Science (Thanks Annette)