The experiments were carried out partly with Mecodrin and partly with neutral tablets of the same form, size, and the same taste (.01 mg sulphate of quinine per tablet). The men received 4 tablets (20 mg), the women 2 (10 mg).
The majority of the volunteers knew that they could receive Mecodrin or control tablets yet not which was given to them, A smaller group was left to believe that they received Mecodrin, although one gave control tablets to some of them.
Among some volunteers the experiments were repeated with random change of the Mecodrin and control days.
Thus we obtained 3 groups: the Normal Group, which received no preparation at all (232 persons), the Control Group, which received only ineffective tablets (121 persons), the Mecodrin Group, which received effective tablets (117 persons).
Although improbable, it is true that the possibility of the symptoms described here [disturbance of sleep] might be explained by volunteers’ prejudices. But this is not entirely excluded under the actual conditions [of our experiment]. Particularly the fact that some 14% of the control group reported diminished fatigue…make it desirable to take steps to counter this interpretation of the experimental results.
As mentioned above, we therefore tried to influence a small group by giving them control tablets and suggesting that they would actually receive Mecodrin. We told them that the tablets would have a slightly stimulating effect, increase their work capacity and general wellbeing, and diminish fatigue. After receiving this [suggestive information], the control group volunteers who actually received Mecodrin showed no significantly different responses from the large [neutrally informed] Mecodrin group.