Jennifer Bosson and Joseph Vandello (associate professors in psychology at the University of South Florida) have put forth the notion of "precarious manhood." Manhood, they posit, is precarious because it is both difficult to obtain and easy to lose. Men, wanting to be perceived of as masculine, often go to great lengths to "prove" their manliness, especially when it has been challenged.
A great deal of research has supported these ideas. Men, when their masculinity is challenged, are more aggressive (e.g., punch a punching bag harder and more frequently), make riskier financial decisions (gamble higher amounts) and avoid behaviors that are stereotypically female (e.g., braiding hair on a doll). Research also shows that gender threats elicit anxiety and stress for men, and that displaying aggression reduces this anxiety. Gender threats in these studies include having men do gender atypical behaviors and setting them up to fail on presumed tests of gender knowledge.
In a recent test of these ideas, T. Andrew Caswell (assistant professor at Gannon University) and colleagues measured men's level of cortisol and testosterone before and after they had either received threatening feedback or gender affirming feedback. They wanted to test if people who naturally are high in testosterone respond with less anxiety - measured using cortisol - when their gender is threatened.