Studies with identical and non-identical twins show that between 50 and 80 percent of one's reported level of happiness is genetically determined.
Moreover, Richard Davidson has found that happy people tend to have more activity in the left frontal cortex while unhappy people tend to have more activity in the right frontal cortex.
Even more striking, whether someone is a cortical righty or a cortical lefty can be read from the foreheads of 10-month infants, and according to Jerome Kagen such left-right determinations that are made from infants predict personality traits through adulthood.
So for those who are still single, unless you want to be stuck with a Debby Downer for a spouse, it would be best to gain access to a brainwave measuring device before proposing marriage.
- The Happiness Hypothesis (2006 book) by Jonathan Haidt, page 33