The study of twins / Peter Mittler.

  • Mittler, Peter J.
Date:
[1971]
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The study of twins / Peter Mittler. Source: Wellcome Collection.

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    80 Cognitive Processes vivid illustration of the complexities of disentangling nature- nurture interactions than the statistical treatment of test re¬ sults of this or any other twin investigation. Unfortunately, biographical evidence is not usually considered of sufficient scientific standing, though Newman's examples generally provide rich confirmation of the psychometric evidence. The latter is briefly summarized in Table 6 for nine of the physical and mental measures on which data were available for all types of twin. Table 6 Correlations for Physical and Mental Tests for MZ Twins Brought Up Together and Apart, and for DZ Twins MZ, MZ^ DZt (N = 50) {N = 19) Source: Newman, Freeman and Holzinger (1937) The table indicates that correlations for physical charac¬ teristics are very similar whether M Z twins are brought up together or apart (except for weight); those for intelligence (Binet and Otis IQ) are somewhat affected by separation, whereas those for educational attainment show the strongest influence of environment. The Binet and Otis IQs (though not the Binet Mental Age) for separated MZ pairs show higher correlations for separated identical pairs than for fraternal pairs brought up together. However, the differences