Thursday, December 7, 2006


Checked various twin studies (there are masses!), and on the whole they confirm that temperament is largely genetic, i.e. any "patterns" are innate ones. Some samples and extracts given below; the web pages give fuller details. So while the form that "bossiness" may take may differ depending upon opportunity - i.e. class differences may come in - the trait itself is not something that comes from the class difference.

Twin research designs and methods are valuable tools for examining genetic and environmental influences on behavioral and medical characteristics.  A review of the biological bases of twinning and descriptions of 10 research designs are presented.  Findings from a selected sampling of twin studies of learning disabilities, personality and temperament, attitudes, psychopathology, and social behavior are summarized.  The findings are discussed with special reference to the activities of mental health practitioners and counselors.
...the shared environment has a very small effect on intellectual development and supports the position that individuals respond to environments in ways consistent with their genetic predispositions.
Evidence indicates that evolutionary theory (e.g., inclusive fitness theory) predicts patterns of social interaction (e.g., cooperation and bereavement) in relatives
Attention to factors influencing cooperation and competition during human social interaction has increased within recent years.  This study tested the hypothesis that higher levels of cooperation would be associated with increased genetic relatedness between interactants, and explored questions concerning the expression of cooperative behavior over time

Assessments of temperament, emotion, cognition, and language acquisition were obtained for 200 pairs of 14-month-old twins. Comparisons between the assessment correlations for identical and fraternal twins indicated an influence of genetics on inhibition, activity, temperament, empathy, negative emotion, spatial memory, categorization skills, and word comprehension. (BC)
In a study of 105 twin pairs, correlations for identical pairs were significantly higher than fraternal pairs on all but one factor: tough-mindedness. Data suggested several components and the total organization of those components of personality and temperament are genetically influenced.
Genetic influences largely accounted for the association between temperament and the sibling relationship. Using identical twin difference scores, sibling cooperation was one aspect of the nonshared environmental influence on temperament
Twin studies of child temperament using objective measures consistently suggest moderate heritability for most dimensions

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