“The amount of dynamic energy and physical strength that a person possesses frequently influences the character of their mental and psychological disposition”
- Kilroy J. Oldster

A study published in Psychological Science conducted by Nicholas Kerry and Damian R. Murray found that differences in physical capital may contribute to sex differences in personality traits among American youth. 

Consistently, personality research has shown that women are generally more neurotic than men. However, despite this finding, not much research can explain the reasoning behind this sex difference. 

As a result, physical strength was investigated as a potential explanation behind this characteristic. 

Two studies involving a total of 878 U.S. students found that differences in physical strength and self-perceived formidability (i.e., the ability to inspire fear or respect due to ones position of power) played a role in sex differences in neuroticism. 

It was also found that grip strength and self-perceived formidability played a noticeable role in determining sex differences in anxiety. That is, those who had greater grip-strength and perceived themselves to be more formidable reported lower levels of anxiety. 

These findings showcase that the sex differences that exist in personality can in fact be partially explained by one’s physical capital.