What makes for a truly merry Christmas? Is your time better spent picking perfect, personalized gifts and decorating your home, or enjoying holiday cheer with family and friends?

For those who celebrate Christmas (and that's about 95 percent of Americans), psychological science can offer some answers — or at least some helpful clues. And for those who don't celebrate Christmas (and I count myself among them), the study of Christmas offers some general lessons about family, gift giving, communication and community. So read on for evidence-based answers to your pressing questions about Christmas.

What makes for a merry Christmas?

A paper published in the Journal of Happiness Studies in 2002 reports a study investigating the experiences of 117 students or residents of Knox County, Ill., during the Christmas season. The researchers found that time spent with family and in religious activities was associated with greater "Christmas well-being," including fewer negative emotions, such as sadness. On the other hand, participating in the materialistic aspects of Christmas, including spending money and receiving gifts, was associated with lower Christmas well-being, including more negative emotion. In addition, spending money was associated with greater stress and receiving gifts was associated with lower ratings for positive moods and emotions, such as interest and enthusiasm.

The authors conclude: "The path to a merry Christmas comes not from purchasing many expensive gifts at the mall, wrapping them, and placing them under the tree, but instead from satisfying deeper needs to be close to one's family and find meaning in life."

When is money an acceptable Christmas gift?

A paper published in the Journal of Economic Psychology in 1991 reports a study of 92 undergraduates at Bristol University in the U.K., who recorded the Christmas gifts they gave and received during their Christmas vacation in 1987. In addition to noting the gifts themselves, the students indicated who they were from or for, and whether money would have been an acceptable alternative. Students' ratings revealed two striking trends related to status and intimacy.

First, money was judged a more acceptable Christmas gift when it came from someone of higher status than the recipient. For example, the students thought it was more acceptable for parents to give their children money as a Christmas gift than for children to give parents or grandparents money as a Christmas gift. For relationships that didn't involve a status asymmetry — like friendships with other students — money was not judged an appropriate gift.

Second, money was less acceptable in an intimate relationship, where the choice of gift offered an opportunity to signal something about the nature of the relationship itself. In particular, a well-chosen gift can take familiarity and effort to select, so opting for money was judged an impersonal, and in some cases inappropriate, alternative. The authors summed up students' reasons for pooh-poohing gifts of money like this: "a gift must possess attributes permitting the communication of love and respect, in keeping with the degree of intimacy and the relative status of donor and recipient."

If you do (or don't) decorate your house for Christmas, what will the neighbors think?

A paper published in the Journal of Environmental Psychology in 1989 reports a study in which 58 undergraduates were shown photographs of the exterior of houses, including a close-up of the entryway and a full view of the home and yard. The houses were either decorated for Christmas or not decorated for Christmas and they belonged to households that reported either high or low cohesiveness with neighbors. Based only on the photos of each house, the undergraduate participants were asked to guess a variety of facts about the residents, including whether they were an integral part of their neighborhood and how likely they would be to know and welcome neighbors into their homes.

Overall, participants rated the residents of houses that were decorated for Christmas as more open and sociable than those that were not. It turns out that for the residents of these homes who had actually reported low cohesiveness with their neighbors, the presence of Christmas decorations made a large and positive difference to perceived sociability. In general, the students expected residents to be sociable when the houses looked "open" and "lived-in." The authors sum up: "Christmas decorations ... can be 'read' by outsiders as evidence of social cohesiveness."

Of course, some aspects of Christmas will likely remain forever beyond the limits of science — like how Santa delivers all those presents in one night. But when it comes to the experience of Christmas and other holidays, we can look to psychological research for insights and guidance on a happy holiday season.

Tania Lombrozo is a psychology professor at the University of California, Berkeley. She writes about psychology, cognitive science and philosophy, with occasional forays into parenting and veganism. You can keep up with more of what she is thinking on Twitter: @TaniaLombrozo

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