And the Double-Blind Shall See Placebo or real medicine?The so-called "double-blind" study, in which neither doctor nor patient is told which kind of pill is being given, is supposed to rid drug studies of the placebo effect, which causes patients to feel better because they think they should.

But in one Texas study, most doctors and many patients correctly guessed -- or figured out -- whether the drug was real or fake.

The two-year study, at the University of Texas School of Public Health in Houston, was set up to test the effectiveness of propranolol, a blood pressure medicine. There were 1,916 patients given the real drug, and 1,921 given placebos.

After the study, doctors were able to guess with 70 percent accuracy which pill their patients were receiving. One clue, the researchers suggest, is that the drug is known to slow heart rate.

And about 80 percent of the patients receiving propranolol correctly guessed they were getting the real drug.

But a majority of the patients receiving placebos -- 57 percent -- said they thought they were getting the real drug, too. The reason for this, the researchers write, "could not be determined but could be a reflection of 'wishful thinking.' "