He touches on something like that in http://www.paulgraham.com/notnot.html http://www.paulgraham.com/notnot.html. The other way to tell an adult is by how the

He touches on something like that in http://www.paulgraham.com/notnot.html http://www.paulgraham.com/notnot.html. The other way to tell an adult is by how they react to a challenge. Someone who's not yet an adult will tend to respond to a challenge from an adult in a way that acknowledges their dominance. If an adult says "that's a stupid idea," a kid will either crawl away with his tail between his legs, or rebel. But rebelling presumes inferiority as much as submission. The adult response to "that's a stupid idea," is simply to look the other person in the eye and say "Really? Why do you think so?" So they test flexibility as a sign on maturity.