It isn't a far stretch to conclude that emotional states of happiness breed nicer traits and behaviors. Think about how you might react to seeing an elderly woman in the grocery store who can't reach a can of beans on the top shelf. If you're a bundle of rage, you might not even notice that she needs help. But if you're having a sunshine and lollipop kind of day, there's probably a greater chance of you stopping to assist her.
So what is it about happiness that compels us to be a little kinder? Positive psychology, or the study of how people can become happier, has drawn correlations between happiness and strong social networks. Generally, people with healthy relationships report the highest levels of life satisfaction [source: Huppert, Baylis and Keverne]. In fact, various studies have shown performing acts of kindness, such as volunteering, bestows the same emotional boost as receiving a doubled salary [source: Huppert, Baylis and Keverne].
Similarly, research indicates that genuine happiness makes for a happier home life. One study tracked the lives of 141 high school seniors into middle age. By examining their yearbook photos, the facilitators determined how happy the students were at the time based on their smiles. Duchenne smiles that cause more muscle contractions in the face reflect authentic joy, while Pan American smiles are rigid and posed [source: Seligman]. Overall, the students with the Duchenne smiles were more likely to be in lasting marriages and have a greater sense of well-being down the road than the Pan American group.
What does this have to do with nice personality traits? The broaden-and-build theory of psychology claims that positive emotions promote innovative ways of thinking and acting. Rather than spiraling downward emotionally, broaden-and-build posits that you climb upward and reach out to others. Likewise, people who are busy volunteering and fostering healthy marital relationships must exhibit nice behaviors along the way. Also, at some point, building social networks depends on reaching out to others and demonstrating goodwill. In short, doing nice things requires -- and produces -- positive emotional states.
In life, it's impossible to always keep a Duchenne smile plastered on your face. Moreover, even the nicest personalities have their tense moments. But just as a genuine smile can brighten someone's day, nice behaviors can elicit happiness in others as well, whether in neurotic New York, extroverted Georgia or anywhere in between.