Throughout history, unsatisfied wives and girlfriends have wondered why their otherwise-perfect male partners roll over and fall straight to sleep after sex instead of engaging in endless chit-chat.A team of researchers from Inserm in France believe they have the answer: it seems that men just can’t help it. Brain scans showed that after orgasm, the thinking area of men’s brains actually shuts down.Other parts then send a message out that the job is done, to let the body know that its interest in sex is no longer required. Then, (just in case even further explanation is needed), the brain is hit with surges of oxytocin and serotonin, nature’s own “shut up and go to sleep” chemicals, rendering dudes all but powerless against the urge to crash.