I'll be teaching about the placebo effect in my quantitative reasoning class later today, and I just remembered having read a year or two ago about a study that claimed to actually disprove the existence of the effect. Do any of you remember this? What is the current scientific consensus about the study? Assuming that the placebo effect is as real as I've always heard it is, I'm also curious whether research on the placebo effect has included variants such as ones where the experimenter tells the subject "The pill I'm giving you is a placebo ...". (There are a variety of ways the explanation could be continued, such as: "There's no reason for it to work, but placebos seem to work, at least for people who think that they're real drugs, and we're trying to see whether the element of conscious deception is required; maybe it's enough to fool the parts of your mind that commune with your immune system." or (less honestly) "A recent study shows that placebos work even for people who know that they're taking placebos; we're just trying to replicate that study, although we're scientifically 100% certain that the study was correct." It would be interesting to know how the effects of such differing scenarios compare.) I myself was in the habit of taking echinacea for most of the '90s, and I made a conscious effort to maximize the placebo effect by trying to convince myself that if I could only convince myself that the capsules were likely to work, they'd be likely to work. But they didn't have any noticeable impact on my colds, and then I read a study that questioned their value, so I stopped taking them. (Of course, the fact that I could be so swayed by a mere *study* explains why echinacea never worked for me: obviously, I hadn't believed in it enough to begin with. :-) ) Jim Propp