Heredity and environment : a critical survey of recently published material on twins and foster children / by R.S. Woodworth ; a report prepared for the Committee on Social Adjustment.

  • Robert S. Woodworth
Date:
[1941]
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Heredity and environment : a critical survey of recently published material on twins and foster children / by R.S. Woodworth ; a report prepared for the Committee on Social Adjustment. Source: Wellcome Collection.

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    develops between them must be due to environment. (Excep tion must be made for certain asymmetries such as right and left handedness. As a single individual shows these asymme tries, it is not strange that a split embryo will sometimes de velop them.) Co-twin control is applicable in various ways. To discover whether imitation plays any part in the child's assumption of the erect posture, one of a pair of identical babies might be prevented from seeing people in that posture until his twin was beginning to stand, the question being whether the isolated twin would stand on his own initiative. This particular experiment has perhaps not been tried but a variety of analogous experiments done in this country and in Russia have been iruitful enough to indicate that the method would be well worth using on a large scale. It was being used on a large scale in the USSR when some political interference put a stop to the project (Levit, 1935; Luria, 1936; Muller, 1 935)- The study of identical twins reared apart belongs under this general head. If they develop differently, environmental factors are responsible, though usually it is not easy to dis cover the exact factors that have produced the difference in in telligence or personality. If separated identicals show greater intra-pair differences than unseparated, again environment is responsible, and again we cannot usually put our finger on the important differentiating factor in the social environment. The whole method could be tuned up by giving it a more ex perimental slant. 1 Social environment of identical and fraternal twins. Re search on the effects of environment may well start with an attempt to discover factors that might probably cause a pair of twins to differ. From a rather external point of view twins, 1 For a review of methods and recent results in twin study, with bibliography of 133 titles, see Carter (1940). [IO]
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