Testosterone and cortisol distributions reveal men's relationship status: Evidence from a study with daily hormone sampling.

Prior studies support men in romantic relationships having lower testosterone and cortisol concentrations than single men. Such studies have generally collected only 1-2 hormone samples per participant, which has left unknown how hormone values are distributed within individuals and whether differences in such distributions can be used to accurately classify men by their relationship status. We collected daily measures of testosterone and cortisol across 31 days from each of 41 young men (N = 1143 observations). Signal detection analyses demonstrated good discrimination of relationship status from subject-mean hormone concentrations. Furthermore, the daily sampling revealed a novel pattern: partnered men almost never experienced high testosterone or high cortisol days. Additional analyses supported replication of prior findings showing positive associations between sociosexual desires and testosterone concentrations among partnered men. These findings are consistent with theoretical models that propose hormonal mediation of tradeoffs between men's mating effort and investment in committed relationships.