Last week, Oxford Dictionary broke the news when it announced its word of the year: emoji. The popular term was then accompanied by a paradoxical emoticon displaying a happy face tearing up. But why do some people really mean it when they say "I'm so happy I'm about to cry"? Science explains why.

Yahoo Health reports a study published in the journal Psychological Science explains the psychology behind "dimorphous expressions", which refers to the combining effects of opposing emotions. Oriana Aragon from Yale University's department of psychology studied the paradox of "cute aggression," where a person becomes so overwhelmed by something that they express their desire to squish it.

According to Aragon, this explanation goes the same with those who tear up when they are happy especially in events like a soldier's homecoming or a bridal march. One obvious reason is that tears of joy are a signal of an intense emotion.

"Expressions are a signal to others that you're overwhelmed, that you need comfort," Aragon told Science of Us. "Even though something great has just happened, you are telling people that you need someone to comfort you. Crying when you're happy arouses consoling behaviors."

Another reason why people have dimorphous expressions is for them to check on their emotions. According to Aragon, those who cry in joy actually swing their emotions back and forth to temper their feelings to normalcy.

Interestingly, those who tear up when they're happy are also the ones who tend to pinch a baby or giggle inappropriately in the middle of a tense exchange. Meanwhile, there's also an explanation for those who could contain their tears or don't even have to.

"People who don't do it just don't get that emotional - they don't reach those emotions," Aragon said. "They just don't express it and it doesn't really matter so long as they can process their emotions."