Association of Assertiveness and fWHR in adult males and females, split by alpha status.

<p>In both sexes a significant positive linear relationship between fWHR and Assertiveness is visible. This relationship held when examining non-alpha individuals only.</p

Linear effects of age and sex on fWHR.

<p>In males, fWHR increases significantly with age, suggesting developmental changes at puberty. In females, fWHR appears to decrease over the lifespan, although no significant change is observed when excluding animals older than 20 years.</p

Illustration of the facial width-to-height ratio: zygomatic width (distance between vertical lines) divided by upper face height (distance between horizontal lines).

<p>Illustration of the facial width-to-height ratio: zygomatic width (distance between vertical lines) divided by upper face height (distance between horizontal lines).</p

Mediation model of sex differences in fWHR by weight.

<p>Mediation model of sex differences in fWHR by weight.</p

Salient loadings of assessed personality attributes on Assertiveness, adapted from Morton and colleagues [32].

<p>Salient loadings of assessed personality attributes on Assertiveness, adapted from Morton and colleagues <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0093369#pone.0093369-Fragaszy1" target="_blank">[32]</a>.</p