How do you measure happiness?

Denmark ranks as one of the happiest countries in the world. See more emotion pictures.

The Danes must be doing something right. In 2008, Denmark ranked as the happiest nation on the planet, according to the World Map of Happiness and the World Values Survey. The same year, the Scandinavian country came in at No. 2 on the World Database of Happiness, barely beat out by nearby Iceland. These happiness surveys polled people around the globe on -- you guessed it -- how happy and satisfied they are with life. Folks in Denmark showed an impressively high degree of social connections, career satisfaction and political and economic stability -- all of which are known to promote happiness [source: Weir and Johnson].

But what does it even mean that the Danish consider themselves happier than a lot of other people around the world? What were the surveys measuring, exactly? According to Webster, happiness is "a state of well-being and contentment." That emotional state the dictionary refers to is arguably different for everyone. At the same time, we know the physical effects of happiness; humans smile and laugh as a natural sign of glee. Certain physiological reactions, such as increased activity in the brain's left prefrontal lobe and decreased amounts of cortisol (a stress hormone) coursing through the bloodstream, happen when we're happy.

Yet, those physical indications of happiness are temporary, just like the feeling of pleasure fades after watching a heart-warming film with friends or opening a birthday present. Evaluating happiness in terms of consistently finding fulfillment in the sum of life's events is harder to grasp. Someone can't communicate it with a single grin or giggle. Consequently, researchers wishing to measure happiness have to go straight to the source.

Quantifying happiness most commonly relies on self-reporting. Happiness surveys such as the Revised Oxford Happiness Scale ask a comprehensive set of questions, while the Satisfaction with Life Scale poses only five. Generally, these polls ask people to rate their satisfaction about various aspects of their lives on a scale. For example, one of the most critical questions asked in the World Values Survey is:

"Taking all things together, would you say you are very happy, rather happy, not very happy or not at all happy?" [source: World Values Survey]

In the here and now, someone may be perfectly content, but who's to say that life won't throw a devastating curve ball in the future? For a more robust happiness gauge, some researchers have gotten a little more personal.