The experimenter effect on results with oral form recognition tests and with tests measuring oral muscular ability

In the introductory part of the present study considerable differences in registrations were found between three different experimenters when an oral form recognition test and an oral muscular-motor test was applied on ten subjects. In the following part recording differences between six other experimenters were evaluated. An intensive training programme was established and repeated twice with those six experimenters during a test period which twenty-eight subjects were tested with the same tests as mentioned above. The results show that in spite of the training programme, uniformity could not be obtained between experimenters. Registration deviations were (1) clearly found for the time results of identifying, (2) less distinctly for registration of subjective judgements of difficulty or for the times of putting together the halves of the test pieces in the test of muscular-motor ability and (3) not at all at the recording of test peice confusions at the oral form recognition test. It was found that the present forms of the training programme alone were not sufficient to gain uniformity between different experimenters but the suitability of prospective experimenters who are supposed to form a common group should be tested by an evaluation of test results found in a real test situation. Experimenters who are clearly deviating, should be replaced by other ones for the task who are more suitable inidividuals. The present study thus emphasizes the previously observed difficulties when clinical observations made by different persons are to be compared.