Page "W. H. R. Rivers" Paragraph 68

It quickly became clear to Rivers, looking in on the experiment from a psycho-physical aspect, that the only way accurate results could be obtained from introspection on behalf of the patient is if the subject under investigation was himself a trained observer, sufficiently discriminative to realise if his introspection was being prejudiced by external irrelevancies or moulded by the form of the experimenter's questions, and sufficiently detached to lead a life of detachment throughout the entire course of the tests.

It was in the belief that he could fulfil these requirements, that Head himself volunteered to act, as Langham puts it, " as Rivers's experimental guinea-pig.