A: Amy looks much younger than her age. At 40, she doesn’t have a wrinkle on her face.

B: Not smiling irons out the wrinkles for her. She even managed to keep a straight face and not smile at the birth of her son.

Note: A straight face is an impassive facial expression that conceals one’s true feelings, especially a desire to laugh. It’s our facial expression when we’re not trying to make a face, like when we are working among colleagues in the office. Comedians are the best at telling jokes with a straight face. A similar phrase is “poker face.” When we play poker, we put on a motionless face so that our opponents won’t be able to tell from our facial expression what kind of hand we have.