# Basic or Adaptation: The Assessment and Heritability of a Brief Measure of Agency

## TL;DR

The study examines whether agency, a personality dimension related to assertiveness, is a basic trait or an adaptation, finding it is moderately heritable and similar to other personality traits.

## Contribution

The paper provides new evidence on the heritability and correlates of agency, comparing it to Big Five traits and generativity.

## Key findings

- Agency is moderately heritable (44.4%) and strongly correlated with extraversion (r = .51).
- Approximately 40% of agency variance overlaps with Big Five traits.
- Agency increases with higher levels of extraversion and openness.

## Abstract

The interpersonal circumplex describes two major axes of personality that guide much of social behavior. Agency, one half of the interpersonal circumplex, refers to relatively stable behavioral patterns that center on self-focused dominance and assertiveness. Past empirical work on agency tends to treat the dimension as a characteristic adaptation, rather than a basic component of personality, in part due to the relatively large gender difference in agency with masculine individuals tending to behave more agentic. However, the psychometric overlap between agency and the most closely linked big five dimension, extraversion, is not well-established, and no behavior genetic work has documented evidence concerning the role of genetic and environmental influences. It is unclear whether agency is more similar to a personality trait, with no evidence of shared environmental influence and moderate heritability, or a characteristic adaptation, with some evidence for shared environmental influence and possibly lower heritability. We used the Midlife Development in the United States study to examine agency, big five, and generativity with replication and robustness check (Nnon-twins = 5,194; Ntwins = 1,914; NMilwaukee = 592). Results indicated that agency was higher in men (d = −.24), moderately heritable (44.4%), strongly correlated with extraversion (r = .51), moderately correlated with generativity (r = .36), and that approximately 40% of the variance in agency was shared with the big five. Agency also changed strongly with extraversion and openness, but less so generativity. Altogether, these results indicate that agency functions similar to other basic personality dimensions but is not clearly a dispositional trait.