If a doctor gives 100 patients who complain of pain a simple sugar pill, he can be sure that 33 of them will feel better. pain experts have known for a long time that people who respond to placebos also get more relief from narcotics than do those who don't show the 'placebo effect'. now research is being done to determine whether the placebo response is all in the head or whether the inert pills have physical effects after all.