A critique of Plomin and Foch's "A twin study of objectively assessed personality in childhood."

Abstract

Plomin and Foch's (1980) study of objectively assessed personality in childhood is critiqued on five points: (a) conceptual validity of the measures, (b) stability of the measures for the population age range, (c) comparability of populations, (d) accuracy of literature review, and (e) appropriate interpretation of broad heritability data. The Plomin and Foch study contains major errors; it is theoretically and methodologically flawed. Their report is especially significant because it is representative of problems critical to the study of the genetic correlates of personality.

Haviland, McGuire, and Rothbaum's "A critique of Plomin and Foch's twin study."

“…In the section "Hereditary Factors Predicted by Questionnaire Methods" (pp. 635-636), Haviland et al (1983) are really arguing with Loehlin and Nichols's (1976) widely cited conclusion:…”

“…Much more impressive, however, is the environmental interpretation of these results. (Plomin & Foch, 1980, p. 685) On page 636 of their article, Haviland et al (1983) begin their attempted attack on "the simple genetic model used by most twin researchers, including Plomin and Foch." Again, this has less to do with our study per se than it does with the field of behavioral genetics as a whole.…”

“…(Loehlin & Nichols, 1976, p. 35). Haviland et al (1983) present a table of a few twin studies using personality questionnaires in which they list the range of identical twin correlations and the range of fraternal twin correlations among the various scales within each study. However, they miss Loehlin and Nichols's point: The issue is not sample fluctuations in the range of identical and fraternal twin correlations but rather "the differences between identical-and fraternaltwin correlations" (Loehlin & Nichols, 1976, p. 86), as quoted above.…”

Further considerations for behavior-genetic analysis of humans.

“…In addition, we briefly describe three relevant issues in experimental behavior-genetic studies as they apply to correlational behavior-genetic studies of human personality. Plomin and Foch (1985) disagree with our presentation of five main points to consider in applying genetic analysis to personality (Haviland, McGuire, & Rothbaum, 1983). The issues raised remain despite Plomin and Foch's claim to the contrary.…”

“…In this reply to Plomin and Foch (1985) we maintain that the five specific points we criticized in their behavior-genetic analysis of personality are still important (Haviland, McGuire, & Rothbaum, 1983). In addition, we briefly describe three relevant issues in experimental behavior-genetic studies as they apply to correlational behavior-genetic studies of human personality.…”