Redheads are twice as likely to avoid the dentist as brunettes or blondes, because a genetic mutation makes them more sensitive to pain and resistant to anesthesia. Presumably they are also more sensitive to having their braids tugged. [NY Times]
I am a redhead, and totally believe this. I think I've developed a high pain tolerance BECAUSE I've slipped out of dental anesthesia a bunch of times, and just sucked it up and had them finish. The last endodontist was horrified that I endured the last half hour of a root canal. Afterward, he kept apologizing and looked like he was going to cry. It was weird.