Question

1. How would the research described in the article affect perspectives on “pathological” aspects of personality?

2. How environmental effects on personality may moderate genetic effects?

3. How might the finding that identical twins are more similar to one another than are fraternal twins be explained with something other than a biological explanation?

Answer 1

1) I think, personality pathology is enduring patterns of cognition, emotion, and behavior that negatively affect a person's adaptation. In psychiatry and clinical psychology, it is characterized by adaptive inflexibility, vicious cycles of maladaptive behavior, and emotional instability under stress.
2) The longitudinal stability of personality is low in childhood, but increases substantially into adulthood. Theoretical explanations for this trend differ in the emphasis placed on intrinsic maturation and socializing influences. To what extent does the increasing stability of personality result from the continuity and crystallization of genetically influenced individual differences, and to what extent does the increasing stability of life experiences explain increases in personality trait stability? Behavioral genetic studies, which decompose longitudinal stability into sources associated with genetic and environmental variation, can help to address this question.Both the genetic and environmental influences on personality increase in stability with age. The contribution of genetic effects to phenotypic stability is moderate in magnitude and relatively constant with age, in part because of small-to-moderate decreases in the heritability of personality over child development that offset increases in genetic stability. In contrast, the contribution of environmental effects to phenotypic stability increases from near-zero in early childhood to moderate in adulthood. The lifespan trend of increasing phenotypic stability, therefore, predominantly results from environmental mechanisms.
3) Identical (monozygotic) twins have attracted special attention for the study of behavior genetics.
Some of the assumptions and results of these studies are reviewed with special attention given
to the natural experiment of identical twins adopted by different families. However, the
correlation for any behavior between the adopted twins of a monozygotic pair is affected by their
common prenatal environment as well as by the pervasive similarity of the two adoptive
environments. The genetic contribution to complex social phenomena, but also to physical
characteristics such as height, is usually overestimated. Both for adopted and unadopted twins
differential effects of cultural, family, and prenatal environments, and the correlated experiences
of twins and their physical appearance affect their development. Taxonomies and samples of
environments need be examined in order to be able to estimate the genetic contributions to
behavioral traits.

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