Chapter 15 - Genetics, Temperament, and Personality

Abstract

This chapter focuses on the genetic bases of temperament and personality. Genetic and environmental influences are separable as components of trait variation. In the context of trait variation, nature can be clearly more influential than nurture and vice-versa. The heritability coefficient is a numerical estimator of the genetic component of trait variation. Estimates of heritability can take one of the two meanings: (1) this meaning is related to narrow-sense heritability. It represents genetic effects transmissible in families. A parent–child correlation on a trait is calculated as one–half the narrow-sense heritability. The narrow-sense heritability has one limitation. It fails to account for possible interactions among genes, which may be located separately in the DNA. Broad-sense heritability removes this deficiency. It is used to estimate all genetic variation contributing to trait variation, including both types of gene-gene interactions. Furthermore, genetic temperament and personality traits are discussed in this chapter. Temperament is the first expression of personality. Modern temperament theorists also focus on infancy, focusing on the first appearance of individual differences in personality. Theorists have differed in their particular definitions of temperament and in their assessment of the main temperamental traits.