According to Som Sommers, author of Situations Matter, we make different faces when we interact with our loved ones. This is only one example of how humans act out of the norm when faced with their loved ones. As we have learned in class, humans have a tendency to conform to behaviors of those around us. When we see others smile, our own soon follows. When we see others frown, it is very likely that we will also frown. However, all these reactions are context-dependent. Sommers explains the conformity phenomenon through the example, "[Why] for a brief period of time, adults who could afford actual shoes instead voluntarily ventured out wearing plastic clogs with swiss-cheese holes."
Despite our mimicking nature, Sommers points out that, "[the] mimicry of frowning faces disappears when the face looking back at you belongs to your partner." Rather than frowning back, in a Dutch study, participants start to smile when shown frowning pictures of their partner instead. Sommers explains the reason why the participants smiled is because they regularly make sacrifices for their partner's well-being. The smile was an automatic effort to, as Sommers states, "soothe their loved one's distress."
http://www.psychologytoday.com/blog/science-small-talk/201112/what-the-face-love-looks
Interesting study! Thanks for sharing it.