Gender shapes and impacts what behaviours people engage in:competition is encouraged for men and punished for women, andespecially vice versa for nurturance. These aspects of gender canhave biomaterial consequences as per the S/P Theory, since com-petitive and nurturant behaviors are hormonally-salient (vanAnders et al., 2011). Gendered forms of engagement in competi-tive and nurturant behaviours might actually lead to differentiallevels of testosterone that overlap with gender/sex, which is why Ihave spoken of “gender?testosterone pathway” (van Anderset al., 2015). Research supports this, with evidence showing thatmany competitive behaviors increase testosterone and many nur-turant ones decrease it
This passage is related to chapter 2's correlation vs. causation. testosterone and a behavior can be related but it doesn't mean that testosterone caused the behavior. The author points out that the relationship can work in both directions.