May 2, 2010

Poor, misunderstood testosterone

De­spite pop­u­lar con­cep­tions about the hor­mone tes­tos­ter­one, in wom­en, at least, the sub­stance ac­tu­ally may pro­mote fair, con­cil­ia­to­ry be­hav­ior, re­search­ers say.

But the myths about tes­tos­ter­one are so pow­er­ful that wom­en in a study started act­ing less fairly if they thought they had re­ceived a dose of it, wheth­er they had or not.

Such are the find­ings of a study ap­pear­ing in the Dec. 8 ad­vance on­line is­sue of the re­search jour­nal Na­ture.

Test­os­terone is often called the “male” hor­mone and is po­pu­lar­ly asso­ciated with aggres­sion. Wom­en have some test­os­terone also, though.

Ernst Fehr of the Un­ivers­ity of Zu­rich, Switz­er­land, and col­leagues set up a bar­gain­ing game in which fe­male par­ti­ci­pants were giv­en a pill ei­ther of tes­tos­ter­one or of a neu­tral sub­stance, called a pla­ce­bo.

Those that re­ceived tes­tos­ter­one showed a “sub­stan­ti­al in­crease in fair bar­gain­ing be­haviour,” lead­ing to better so­cial in­ter­ac­tions, the re­search­ers wrote. But wom­en who thought that they re­ceived tes­tos­ter­one, wheth­er or not they ac­tu­ally did, “be­haved much more un­fair­ly” than those who thought that they re­ceived pla­ce­bo.

So, the neg­a­tive, an­ti­so­cial con­nota­t­ion of in­creas­ing tes­tos­ter­one lev­els seems to be strong enough to in­duce neg­a­tive so­cial be­hav­iour even when the bi­o­log­i­cal re­sult is ac­tu­ally the op­po­site, the sci­en­tists re­marked.

Ev­i­dence from an­i­mal stud­ies does show that tes­tos­ter­one causes ag­gres­sion to­ward oth­er mem­bers of the spe­cies, Fehr and col­leagues wrote. Pop­u­lar wis­dom tends to as­sume hu­mans work the same way. But it has been un­clear wheth­er this is cor­rect.

Stud­ies have in­deed found that male and fe­male pris­on­ers with vi­o­lent his­to­ries have high­er sal­i­vary tes­tos­ter­one lev­els than nonvi­o­lent pris­on­ers, the re­search­ers not­ed. But this does not show that the tes­tos­ter­one ac­tu­ally caused the vi­o­lence.

A com­pet­ing idea, they ob­served, is that tes­tos­ter­one mo­ti­vates peo­ple to seek high so­cial sta­tus. De­pend­ing on the situa­t­ion, they may try to achieve that ei­ther through vi­o­lence or through fair­ness.

In the con­text of the ex­pe­ri­men­tal bar­gain­ing game, fair­ness tended to help pro­tect so­cial sta­tus, ac­cord­ing to Fehr and col­leagues.

In the “ul­ti­ma­tum game,” as it was called, two play­ers are pre­sented with a sum of mon­ey, which they can keep if they can agree on how to split it. The catch is that just one play­er gets to pro­pose—and only on­ce—how it should be di­vid­ed. The oth­er play­er must ac­cept or re­ject that of­fer. “Fair” of­fers, such as an even split, tend to be more readily ac­cepted than “un­fair” of­fers where the pro­pos­er tries to keep most of the mon­ey. Fehr and col­leagues sug­gested that tes­tos­ter­one mo­ti­vat­ed play­ers to pro­pose “fair­er” of­fers in or­der to avoid the so­cial af­front of re­jection.

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