WATERVILLE, ME–Cori Schmidt, 12, went through a life change Tuesday, moving from the giggling-at-everything stage of adolescence to the never-smiling stage. "My goodness, just the other day, I accidentally left a pair of old pantyhose on the couch, and she was jumping all over the living room giggling hysterically," Hannah Schmidt, 41, said of her maturing daughter. "But now, everything I say to her is met with a gloomy scowl." Asked if she was aware of her passage into sullenhood, the younger Schmidt said, "I don't know," without making eye contact.