We like people who look like us, because they tend to have personalities similar to our own. And, a new study suggests, the longer we are with someone, the more similarities in appearance grow. Researchers set out to study why couples often tend to look like one another. They asked 11 male and 11 female participants to judge the age, attractiveness and personality of 160 real-life married couples. Photographs of husbands and wives were viewed separately, so the participants didn't know who was married to whom. The test participants rated men and women who were actual couples as looking alike and having similar personalities. Also, the longer the couples had been together, the greater the similarities. The researchers guess that the sharing of experiences might affect how couples look. The idea that there is a connection between appearance and personality might seem strange at first, but there could be biological reasons for a link, said study member Tony Little from the University of Liverpool in England. "The face displays our emotions and over time, emotional expressions may become written in the face," Little told Live Science. For example, someone who smiles a lot may develop lines and muscles that are suggestive of someone who is happy. Other studies have shown that partners who are genetically similar to each other tend to have happier marriages. The new study indicates that people have different features when using facial appearance to make decisions about someone's personality, and that the particular cues  focused on change from face to face. Vital to the decision, however, are eyes and smiles. "Smiles are important social cues that may tell us whether or not someone is friendly, and eyes are also a traditional focus of attention," Little said. Overall face shape can be important too. For example, the combination of large chins and strong brow ridges can create an impression of disagreeableness and being unwilling to cooperate, Little said. Which part of a person's face can help you judge whether he/she is paying attention to you?
Eyes. Nose. Mouth. Eyebrow.