The pitfalls of "mental tests" / by Charles S. Myers.

  • Charles Samuel Myers
Date:
[1911?]
Catalogue details

Licence: In copyright

Credit: The pitfalls of "mental tests" / by Charles S. Myers. Source: Wellcome Collection.

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    data with the help of an army of untrained observers. I have heard it confidently asserted that the gross errors inevitably arising from inaccuracies and inconsistencies of procedure among different observers cancel one another in the long run of such vast numbers of measurements. Nothing, I think, can be more dangerous or false than this idea that the untrustworthiness of crude methods diminishes as the number of observers increases. It involves the assumption that in the long run errors occur to an equal extent in opposite directions—a most unlikely hypothesis. Individual differences in mode of measurement are great enough even in anthropometry, despite the standardization of measurements. There is, I believe, a well-founded rumour that when the pigmies visited this country and were independently measured by several observers well practised in anthropometry, the results obtained by these observers were startlingly divergent. If this be so, the sooner the fact is put on record the better for the future security of anthropometry. In any case I am sure that hitherto it has not been adequately realized how untrustworthy is a comparison between the measurements obtained by different observers upon the same individual. I can only give one or two actual examples, but these, perhaps, are sufficiently striking. Professor Cunningham and Mr. Browne measured the heads of several anatomists at a meeting of the Anatomical Society some years ago. One of their subjects gave a head length of 198 mm. and a head breadth of 147 mm.—that is, a cephalic index of 74*24. The same individual happened to be measured sub¬ sequently by Miss Alice Lee, fully as competent an observer, who obtained a head length of 195 mm. and a head breadth of 150 mm.—that is, a cephalic index of 76*92. Thus there was a divergence of over 3*5 per cent, in the values of the index obtained from the same individual by these observers, although each claimed to be taking precisely the same measurements—the maximal head length and the maximal head breadth.
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