Behave: The Biology of Humans at Our Best and Worst

by Robert M. Sapolsky

So testosterone does subtle things to behavior. Nonetheless, this doesn’t tell us much because everything can be interpreted every which way. Testosterone increases anxiety—you feel threatened and become more reactively aggressive. Testosterone decreases anxiety—you feel cocky and overconfident, become more preemptively aggressive. Testosterone increases risk taking—“Hey, let’s gamble and invade.” Testosterone increases risk taking—“Hey, let’s gamble and make a peace offer.” Testosterone makes you feel good—“Let’s start another fight, since the last one went swell.” Testosterone makes you feel good—“Let’s all hold hands.” It’s a crucial unifying concept that testosterone’s effects are hugely context dependent.