Women should smile more. Men should keep a poker face.
“Happy girls are the prettiest”
― Audrey Hepburn
According to a study conducted by the American Psychological Association, smiling or happiness is the most attractive expression on women while pride (I interpret this as a show of confidence), unexpectedly is the most attractive male expression. The study covered a wide age range, thus proving that this fact on what expression makes a specific gender more attractive holds true both on young and adult.