[cLeEOGPw]

What do you mean "on request"? Because if someone asked me to fake a smile I would not even try to look sincere either. Deficient practice in imitation can be considered when a person actually wants to look like he's smiling sincerely, but for us it is the opposite. And we don't "suppress" smile - we do not feel any need to smile for random strangers. Unless you want to look offensive. Especially fake smile. Fake smile is mostly used by people who want something from you and are willing to be very annoying about it - usually want something bad to sell or somehow screw you over. I have no idea why are you coming up with those ridiculous theories about reflexes when there are very good reasons not to smile and not to fake smile to random people, and to smile to friends.