Testosterone and androgen receptor gene polymorphism are associated with confidence and competitiveness in men

Stud­ies in non-hu­man an­i­mals and hu­mans have demon­strated the im­por­tant role of testos­terone in com­pet­i­tive in­ter­ac­tions. Here, we in­ves­ti­gated whether en­doge­nous testos­terone lev­els pre­dict the de­ci­sion to com­pete, in a de­sign ex­clud­ing spite as a mo­tive un­der­ly­ing com­pet­i­tive­ness. In a lab­o­ra­tory ex­per­i­ment with real mon­e­tary in­cen­tives, 181 men solved arith­metic prob­lems, first un­der a non­com­pet­i­tive piece rate, fol­lowed by a com­pe­ti­tion in­cen­tive scheme. We also as­sessed sev­eral pa­ra­me­ters rel­e­vant to com­pe­ti­tion, such as risk tak­ing, per­for­mance, and con­fi­dence in one's own per­for­mance. Sali­vary testos­terone lev­els were mea­sured be­fore and 20 min af­ter the com­pe­ti­tion task us­ing mass spec­trom­e­try. Par­tic­i­pants were also geno­typed for the CAG re­peat poly­mor­phism of the an­dro­gen re­cep­tor gene, known to in­flu­ence the ef­fi­cacy of testos­terone sig­nal­ing in a rec­i­p­ro­cal re­la­tion­ship to the num­ber of CAG re­peats. We ob­served a sig­nif­i­cant pos­i­tive as­so­ci­a­tion be­tween basal testos­terone lev­els and the de­ci­sion to com­pete, and that higher testos­terone lev­els were re­lated to greater con­fi­dence in one's own per­for­mance. Whereas the num­ber of CAG re­peats was not as­so­ci­ated with the choice to com­pete, a lower num­ber of CAG re­peats was re­lated to greater con­fi­dence in those who chose to com­pete, but this ef­fect was at­trib­ut­able to the poly­mor­phis­m's ef­fect on ac­tual per­for­mance. An in­crease in testos­terone lev­els was ob­served fol­low­ing the ex­per­i­ment, and this in­crease var­ied with self-re­ported high-school math grades. We ex­pand upon the lat­est re­search by doc­u­ment­ing ef­fects of the an­dro­gen sys­tem in con­fi­dence in one's own abil­ity, and con­clude that testos­terone pro­motes com­pet­i­tive­ness with­out spite.