Voluntary Participation
Experiments on persons who offer themselves voluntarily have always been considered admissible. In literary works care is always taken to note this voluntariness; where it is not mentioned, one may conclude that it was nonexistent.
The interest taken in the voluntariness of the person experimented upon has various reasons.
First of all the compulsory experiment—in contrast to the voluntary experiment—means an additional, very heavy mental strain, for the experimenter since the health and life of a human being may be at stake and the future existence of the person experimented upon may be imperiled.
But the experimenter has not only a purely human interest in having the person to be experimented upon offer himself with a certain voluntariness; in many cases he must absolutely depend on the cooperation of the person experimented on; he needs truthful information about observations made during the experiment, which cannot otherwise be carried out properly. Compare for instance the high-altitude and sea-water experiments.
Finally there may exist the wish to be protected against claims for damages and to prevent the uncovering of legal provisions, as well as to guard against the possible political odium that might result from having given orders for a forced experiment.
However, one look at the literature shows that the notion of voluntariness is strongly suspect, and every critical reader will in most cases associate himself with such suspicions.
The subjection to an experiment which is dangerous or even only painful or temporarily onerous must be based on a special motive.
Ethical reasons alone can give rise to voluntariness strictly speaking only in the case of the researcher himself, that is in self-experiments, and in the case of persons who for ethical reasons consciously wish to support by their cooperation the aims of the researcher.