At the interface of social cognition and psychometrics: Manipulating the sex of the reference class modulates sex differences in personality traits

• Researchers have concluded that sex differences in personality are minimal.
• Hypothesis: People are biased toward self-assessing traits relative to same-sex others.
• Sex differences were similar when self-assessing relative to unspecified vs. same-sex others.
• When self-assessing relative to opposite-sex others, sex differences were much larger.
• Conclusion: A same-sex comparison bias may impact measurement of sex differences.

Psychometric surveys suggest that sex differences in personality are minimal. Herein, we argue that (a) the mind is likely biased toward assessing oneself relative to same-sex others, and (b) this bias may affect the measurement of sex differences in personality. In support of this, an experiment demonstrates modulation of sex differences on the HEXACO facets by manipulating the sex of the “reference class”—the group of people subjects compare themselves to when making self-assessments on survey items. Although patterns varied across traits, sex differences were relatively small in the “unspecified” and “same-sex” reference class conditions—but substantially larger in the “opposite-sex” condition. These findings point to a same-sex comparison bias that may impact the measurement of sex differences in personality.