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Altruism and aggression: the heritability of individual differences
Journal of Personality and Social Psychology
|June 1, 1986
Summary
Genetic factors significantly influence altruistic and aggressive behaviors, with heritability estimates around 60%. Environmental influences are primarily unique to individuals, not shared family environments. Altruism increases with age, while aggressiveness decreases, and women score higher on altruism than men.
Area of Science:
- Behavioral Genetics
- Psychology
- Twin Studies
Background:
- Understanding the genetic and environmental underpinnings of social behaviors is crucial.
- Twin studies provide a powerful method for disentangling these influences.
Purpose of the Study:
- To investigate the heritability of altruistic and aggressive tendencies.
- To examine the roles of genetic, shared environmental, and unique environmental factors.
- To explore age and sex differences in these behavioral traits.
Main Methods:
- Utilized data from 573 adult twin pairs.
- Administered five questionnaires assessing altruism, empathy, nurturance, aggressiveness, and assertiveness.
- Employed intraclass correlations and maximum-likelihood model-fitting for heritability estimation.
Main Results:
- Broad heritability estimates ranged from 56% to 72% for the measured traits.
- Approximately 50% of variance was attributed to genetic effects, with negligible shared environmental influence.
- Altruism scores increased with age (19-60), while aggressiveness scores decreased.
- Women exhibited higher altruism and lower aggressiveness scores than men.
Conclusions:
- Both genetic and unique environmental factors significantly shape altruistic and aggressive behaviors.
- Shared family environment plays a minimal role in the development of these tendencies.
- Observed age and sex differences suggest distinct developmental trajectories and social influences.