It has long been known that happiness depends on many different life circumstances.
Now scientists have developed a mathematical equation that can predict momentary delight.
They found that participants were happiest when they performed better than expected during a risk-reward task.
Brain scans also revealed that happiness scores correlated with areas known to be important for well-being.
For the full story, click here (http://www.bbc.com/news/science-environment-28592838).