Participation in so-called high risk, extreme or adventure sports has grown significantly in the last decade. Whether they’re big wave surfing, mountaineering, desert running, BASE jumping or free diving, more people are chasing an adrenaline high and sometimes dying in the process. Psychologists, sociologists, anthropologists and neuroscientists say the motivation is not a death wish, but rather a yearning to feel alive — which reveals much about us as a society.