Well, adventuresome rats, anyway, according to this recent study.
“… novelty-averse laboratory rats, after reaching maturity, died at markedly younger ages than did their more adventurous comrades. Heightened hormone responses to mildly stressful events throughout life ultimately undermined the capacity of the inhibited rats to resist tumors and other health threats, contend Sonia A. Cavigelli and Martha K. McClintock, both psychologists at the University of Chicago.”
Even the above Science News article warns of the dangers of over-applying this to humans, of course–and points out that risky behavior already has a known track record of causing humans to die young. Still, something interesting to ponder.
Myself, I seem to be made up of equal parts wanting to take on the world and wanting to hide under the bed. But am happier when the former impulse gets the upper hand.