Case closed? Not exactly.
There's still the question of how much our happiness depends on genetics, and how much it is affected by our lifestyles and possessions.
The researchers have come up with a formula that they have used in a number of publications. It's 50 percent genetics. The circumstances we find ourselves in -- like where we live, the quality of our love lives, whether we have a few bucks in the bank -- account for only about 10 percent. The remaining 40 percent is "within our control, how we think and behave."
But where did those numbers come from?
"Basically, we kind of made them up," Sheldon said, adding quickly, "but not entirely."
The 50 percent genetics is based on other research of identical twins who were separated at birth and had no contact with each other. A huge study in Germany found that separated twins ranked almost exactly the same on the happiness scale, regardless of their personal experiences.
"And if you look at studies of various superficial circumstances, like income, where you live, how many cars you have, those are pretty small," Sheldon said. "They don't seem to account for more than about 10 percent.
"So that left 40 percent that we conclude, although not everybody would agree with this conclusion, is the percent that is affected by what you do."
That certainly indicates that our happiness can be greatly influenced by what we do, and if the number is anywhere near correct, simple changes, like appreciating what we already have, can make a significant difference in our level of happiness.
But if that number is way off, as many psychologists would contend, then there isn't a lot we can do to make us keep smiling. Still, it may be worth a try.