Polygenic Behavioral Characteristics and Epigenetics

Polygenic Behavioral Characteristics in Humans

Overview of Polygenic Traits

Most measures of human traits that are of interest to psychologists, such as scores on personality tests, are not discrete but rather continuous and normally distributed. These traits are influenced by multiple genes in addition to various environmental variables.

Influence of Genetics and Environment on Behavioral Traits

Psychologists strive to determine the extent to which variations in such scores within a specific group of individuals arise from genetic differences versus variations in environmental experiences. Understanding the contribution of genes versus environment is essential in psychology.

Methodological Approaches to Estimate Genetic Influence

Given that psychologists cannot conduct selective breeding studies on human populations ethically, they have devised alternative methodologies to estimate the degree of genetic influence on human traits. This involves comparing the average differences in test scores between individuals who are genetically closely related to those who are genetically less closely related.

Twin and Sibling Studies

The most effective comparative methods utilized are those involving:

  • Identical twins versus fraternal twins

  • Biologically related siblings against adoptive siblings
    These comparisons are particularly insightful because identical twins share nearly all their genetic material, while fraternal twins share about 50% on average. In contrast, the environments of closely related individuals are controlled in such a way that they are not significantly more similar than those of individuals who are less closely related.

Application of These Methods

Psychologists will later apply these genetic comparison methods to a wide variety of psychological subjects, including but not limited to:

  • Intelligence tests

  • Personality tests

  • Predispositions to various mental disorders
    These applications help clarify the genetic versus environmental influence on psychological traits.

Epigenetics: Gene Regulation

Definition and Importance

Epigenetics refers to the mechanisms that explain how genes are turned on and off, influencing how certain genetic predispositions may express themselves under different environmental conditions.

Research Developments

Significant research has been conducted to understand these epigenetic effects, contributing to a broader understanding of gene expression in the context of psychological and behavioral traits. Research as recent as 2014 and 2016 have implicated stress and other environmental factors in altering gene expression, which can lead to different behavioral outcomes.