Park, Lee C. & Covi, Lino (1965). Nonblind placebo trial: an exploration of neurotic patients' responses to placebo when its inert content is disclosed. Archives of General Psychiatry, 12(4), 336-345.
Doctors told their patients they were receiving a placebo by reading the following script:
Mr. Doe, at the intake conference we discussed your problems and your condition, and it was decided to consider further the possibility and the need of treatment for you before we make a final recommendation next week. Meanwhile, we have a week between now and your next appointment, and we would like to do something to give you some relief from your symptoms. Many different kinds of tranquilizers and similar pills have been used for conditions such as yours, and many of them have helped. Many people with your kind of condition have also been helped by what are sometimes called “sugar pills,” and we feel that a so-called sugar pill may help you, too. Do you know what a sugar pill is? A sugar pill is a pill with no medicine in it at all. I think this pill will help you as it has helped so many others. Are you willing to try this pill?
14 patients stayed in the study, and all 14 reported improvement. Their attitudes were as follows:
- 8 patients believed the pills were placebos (3 with “absolutely certainty”)
- 6 patients believed the doctors lied (2 with certainty)
- 5 believed the benefits were caused by a drug
- 9 believed they were helped by placebo, by the doctor, or by themselves