Romantic relationships are challenging, rewarding, confusing, and exhilarating–sometimes all at the same time.

Should you take things slowly at the beginning or dive right in? Can things stay hot in the bedroom even after years of being together? What happens when one of you wants to use a holiday bonus to invest in Bitcoin and the other wants to go on a vacation?

The answers aren’t always clear, but when it comes to marital satisfaction, science has some interesting things to offer.

According to research, the happiest couples are those who:

1. Don’t fight over text

What seems obvious is now backed up by science: a study out of Brigham Young University shows that couples who argue over text; apologize over text; and/or attempt to make decisions over text, are less happy in their relationships.

When it comes to the big stuff, don’t let an emoji take the place of your actual face.

2. Don’t have kids

Children are one of the most fulfilling parts of life. Unfortunately, they’re hell on relationships. Numerous studies, including a 2014 survey of 5,000 people in long-term relationships, show that childless couples (married or unmarried) are happiest.

This isn’t to say you can’t be happy if you have kids–it’s just to understand that it’s normal to not feel happy sometimes. Many couples put pressure on themselves to feel perfectly fulfilled once they have what they’ve always wanted (a long-term partnership with children), but the reality of kids is that they’re very stressful on relationships.

3. Have friends who stay married

If you’re the average of the five people you spend the most time with, you’re also just as married as them.

According to research out of Brown University, you’re 75 percent more likely to get divorced if a friend or close relative has already done the deed. When it’s someone one more degree of separation out (the friend of a friend), you’re 33 percent more likely to get divorced.

Researchers had this to say on the ramifications of the results: “We suggest that attending to the health of one’s friends’ marriages might serve to support and enhance the durability of one’s own relationship.”

4. Fight at the beginning, then not a lot

Psychologists like Dr. Herb Goldberg suggest that our model for relationship is backwards–we tend to expect things to go smoothly at the beginning, and for problems (and conflicts) to arise later. In fact, Dr. Goldberg argues that couples should have “rough and ragged” beginnings where they work things out, and then look forward to a long and happy incline in the state of the relationship.

Research agrees: a Florida State study found that couples who are able to be openly angry in the beginning are happier long-term. According to lead researcher James McNulty, the “short-term discomfort of an angry but honest conversation” is healthy for the relationship over the long haul.

5. Are comprised of one first-born child and one last-born child

There’s an entire body of research on how your birth order impacts your life, including your relationships as well as professional success. One of the happiest pairings for couples? Someone who was the youngest child with someone who was the oldest.

Researchers hypothesize this may be because the relationship has one person who enjoys being taken care of, and one who’s used to taking care of others.

6. Know who does what when it comes to housework

According to a UCLA study, couples who agree to share chores at home are more likely to be happier in their relationships. An important caveat: couples who have clearly defined responsibilities are far more likely to be satisfied.

In other words, when you know what to do and what’s expected with you, you tend to be happier both yourself and with your spouse. This might be a good thing to sit down and discuss in the new year, especially if you’re newly cohabitating.

7. Are gay–or straight and feminist

In a recent study of 5,000 people, researchers found that gay couples are “happier and more positive” about their relationships than their heterosexual counterparts. Straight couples made less time for each other, and were less likely to share common interests and communicate well.

If you’re going to be hetero, though, you’re better off being feminist. Research out of Rutgers shows that both men and women with feminist partners are more satisfied in their (hetero) relationships. The name of the study? Feminism And Romance Go Hand In Hand.

8. If hetero, are comprised of a lovely lady and a not-as-lovely man

Levels of attractiveness within couples has long been the subject of debate (not to mention song lyrics). According to a study in the Journal of Personality and Social Psychology, when husbands view their wives as the more attractive of the pair, not only are they more satisfied in the relationship, but the wives are, too. The opposite was not true–when husbands thought they were better-looking, they weren’t as happy.

9. Are best friends

The National Bureau of Economic Research did a study demonstrating that marriage, on the whole, leads to increased levels of happiness (they controlled for premarital happiness).

Perhaps more telling was the finding that people who consider their spouse to be their best friend are almost twice as satisfied in their marriages as other people.

“What immediately intrigued me about the results was to rethink marriage as a whole,” researcher John Helliwell said. “Maybe what is really important is friendship, and to never forget that in the push and pull of daily life.”

10. And have a lot of friends in common

In 2013, Facebook released a report that analyzed 1.3M of its users, looking at, among other things, relationships. The conclusion? Couples with overlapping social networks tended to be less likely to break up–especially when that closeness included “social dispersion,” or the introduction of one person’s sphere to the other, and vice versa.

In other words, the best-case scenario is when each person has their own circle, but the two also overlap.

11. Spend money in similar ways

The two biggest things couples fight about are sex and money. When it comes to the latter, it’s well-known to psychologists as well as social scientists that for some reason, people tend to attract their spending opposite. Big spenders tend to attract thrifty people, and vice versa.

A University of Michigan study corroborated this. Researchers found that both married and unmarried people tend to select their “money opposite”–and that this causes strife in the relationship. The happiest couples tend to spend money in a similar way, whether that is saving or indulging.

12. Have sex at least once a week

Probably the best statistic of the bunch comes from a 2004 study, which showed that upping your sexual activity from once a month to once a week can cause happiness levels to jump by as much if you made an extra $50,000 a year.

The study, entitled “Money, Sex, and Happiness: An Empirical Study” sampled 16,000 adult Americans. One of its main conclusions: “[S]exual activity enters strongly positively in happiness equations.”

13. Celebrate each other’s achievements

Anyone who has been in a relationship can attest to this one, but now there’s research to confirm it: A study in The Journal of Personality and Social Psychology showed that when couples celebrate their partner’s accomplishments as if they were their own, they’re more satisfied in the relationship.

“In good times and bad” includes the good times–something it can be easy to forget. And it’s true; there’s nothing quite so satisfying as having your partner be loudly and enthusiastically in your corner when you do well.

Joy, after all, multiplies with love.