Robert Zajonc (rhymes with science) was one of the most innovative psychologists of the last 50 years and contributed much toward understanding emotions and how our thoughts shape our emotional lives. His experiments revealed the mere exposure effect which shows that repeated exposure to any new object increases our liking of that object. Check out this demonstration of the effect here.
He also proposed that people, often unconsciously, mimic the facial expressions of their spouses and that, over the years, couples who tend to share similar facial expressions will become increasingly similar in appearance.
Based on the assortitative mating activity we did in class you might think that couples are initiatially drawn to each other who are similar in attractiveness and may even share certain facial features but this is not what Zajonc found in his experiments. Here is a NY Times article reporting on the original finding and the methods used to arrive at this conclusion.
Now conjure an image of the person you are currently dating or interested in. Do you really want to look like that person 25 years from now?!
Another facial expression that signals emotion and often reveals the stirring of the heart for another, or perhaps just plain old embarrassment is the blush.
Recent studies have found that blushing can help reduce criticism from others and increase social bonds.
Your textbook also describes how knowing someone else is fond of you can increase attraction. This seems rather obvious and yet researchers have found that not knowing whether or not someone likes you at all can be an even more potent factor toward attraction.
How many of you already act indifferently toward a potential boy/girl friend when you really are head over heels?