To cohabitate or not to cohabitate? It’s a question many couples ask. Living together can be an attractive prospect for obvious reasons. Share more of your life with someone you love? Sure! Split living expenses and responsibilities for household chores or pet care? Sign me up!

But couples may be less inclined to think or talk about what happens to their sex lives once they move in together.

The good news for unmarried couples who live together is research shows they tend to have more sex, on average, than their married counterparts.

The bad news?

Some research suggests that satisfaction with sex may lower for the unmarried cohabitators.

From a psychological perspective, what might explain this sexual slump post move-in? And why might sex be better when you don’t share the same roof? Well …

Familiarity breeds disinterest.

Let's tap into our Neanderthal brains for a moment. We need to consider that from an evolutionary perspective, we like familiarity. Familiar equals safe and safe equals higher odds of reproductive success. Now, from a different psychological stance, prolonged familiarity can also lead to boredom, lack of interest, and even aversion.

An all-avocado-toast-all-the-time diet may start out pretty delicious, but after two straight weeks that rich, green goodness may start to seem mushy and tasteless. Sure, humans aren’t avocado toast (unfortunately), but the point is familiarity plays an important role in boosting our initial attraction to our partners. It can also lead to a disinterested and dozy attitude to sex over time.

Scarcity is sexy.

Have you ever had your heart set on trying that brand new restaurant only to find there are no reservations in sight for the next two months? Well, it must be pretty fantastic then, right?

Research on consumer behaviour suggests that perceived scarcity increases desirability. If we translate this into sexual economic terms, couples who don’t live together may view sex as more of a commodity. As a result, it seems more appealing. Cohabitating couples, with a steady supply of their sweatpant-wearing, chip crumb-sporting partner, may not view sex as quite as much of a hot commodity.

Passionate to companionate.

New relationships (or at least the exciting ones) have the "can’t eat, can’t sleep, want you all the time" quality. Welcome aboard the rollercoaster of passionate love. With time, the rollercoaster eventually morphs into a minivan of companionate love.

Psychologists characterize this type of love by trust, emotional intimacy, and commitment. Sure, it’s not as fiery or emotionally intense as passionate love, but it’s the glue that develops over time that helps keep couples together. Cohabitating couples may be making the transition off the rollercoaster into the minivan. This can be great news for relationship depth, but it may come at the expense of sexual passion.

More partner, more problems.

Living together can put a magnifying glass on problems that predated shacking up — or create new ones altogether. Finding out your partner insists on alphabetizing the spice rack or thinks cleaning the bathroom is reserved for occasions like Christmas and Easter can add strain to a relationship and sex life. This is especially the case if couples haven’t established healthy communication patterns. Attempting to mind-read, failing to check in about assumptions, and withdrawing in response to conflict can add fuel to fire, whether you’re arguing about sex or the spice rack.

So what’s the solution for the cohabitators?

Sure, you can start wearing a disguise and make yourself scarce. But a less creepy approach might be a good old-fashioned conversation about sex or other unspoken resentments. Being intentional and proactive about the whens and whats of sex can’t hurt either. Contrary to societal scripts about sex, good sex doesn’t just continue to be good over time without discussion and planning.

Finally, perhaps we all need reminding that rollercoasters are fun but taking the minivan home to watch Netflix together ain’t bad either.