Steve Cannane, journalist and broadcaster, examines risk. Everyone likes a thrill but teens take it to the next level. The more dangerous a dare, the more crazy a stunt, teens just can't get enough of risk-taking. Scientists are now realising that risk-taking is actually a crucial phase of adolescence. By taking risks we force our brains to make decisions which allow our brains to grow. The adult brain isn't fully formed until well into a person's twenties. This period of growth is central to carving out the future individual adult. But it also means that certain regions of the brain are still under construction. The brain's "brakes" don't yet work, which lead teens to making some poor decisions.