Evidence for the stress-linked immunocompetence handicap hypothesis in human male faces

Abstract

The stress-linked immunocompetence handicap hypothesis (SL-ICHH) of sexual selection incorporates a role of the stress hormone corticosterone (C; cortisol in humans) in relationships between testosterone (T), immunity and secondary sexual trait expression. In support of this, C has been shown to mediate and moderate relationships between T and immune response and to be inversely related to attractiveness in some avian species. We predicted that female preferences for cues to T in human male faces would be contingent upon co-occurring cortisol levels. In study 1, we tested relationships between T and cortisol and attractiveness, masculinity and health ratings of raw male faces. We found cortisol to be inversely related to attractiveness. In study 2, we tested female preferences for male faces that were parametrically manipulated on the basis of cues to naturally co-occurring levels of T and cortisol across the menstrual cycle. Women preferred cues to low cortisol in general and in the fertile phase of the cycle, and there was an interaction between T and cortisol in general and in the non-fertile phase. Results were consistent with the SL-ICHH but not the original immunocompetence handicap model: females expressed preferences for cues to cortisol but not for cues to T, except in interaction with the stress hormone. Results inform the SL-ICHH by demonstrating female preferences for low cortisol and the nature of its interaction with T in humans, as well as indicating the traits that may be signalled by different combinations of the hormones including immune response, current health and resource acquisition characteristics.

Glucocorticoids in Mate Choice

“…Once again, women preferred the faces of males with low cortisol, and didn't express preferences for testosterone. In this second study, we also tested the effects of the hormones on perceived dominance and health, finding that low cortisol faces were also rated as more dominant and healthy than high cortisol faces [26,27]. The findings of both studies are consistent with work in other species that shows that females prefer males with low levels of glucocorticoids.…”

“…We concluded that women can detect cues to cortisol in the male face, and that low cortisol is desirable in a male partner. We also suggested that low cortisol may be associated with beneficial heritable characteristics as women expressed the strongest preferences for facial cues to low cortisol at times when they were most likely to conceive [26]. We replicated this pattern of results in a different sample of faces with a novel sample of female raters, again recruited from UK student populations.…”

“…There is evidence that cortisol (the primary human glucocorticoid) and testosterone are positively correlated [25], although this finding is not consistent (see for example [26,27]) and may depend upon, for example, the intensity of recent exercise [28]. Sexually dimorphic facial characteristics derive from sex differences in the ratio of the male and female sex hormones that emerge at puberty (see for example [29]).…”

“…We proposed that high testosterone males (i.e. those signalling the strength of their immune system) are better able to cope with the detrimental effects of stress [26,27]. In order to test this explanation, however, it is necessary to experimentally manipulate stress in males who differ in their level of testosterone and test for any divergent effects on immune system and/or sexual signals.…”

Sexual selection on male vocal fundamental frequency in humans and other anthropoids

“…Steroid hormones may provide a link between F 0 and condition. Growing evidence indicates that glucocorticoids such as the stress hormone cortisol negatively interact with testosterone in predicting immune function and influencing the expression of secondary sex traits [25][26][27]. Infection stimulates cortisol production [28], which downregulates androgen receptors and inhibits the action of testosterone on target tissues [29][30][31][32][33].…”