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Happy couples are the ones who have lots of sex. At least that's what we've been so often told, and there is some scientific grounds for this, with plenty of studies showing that couples who have more sex are also happier, both as individuals and in their relationships. 

Researchers from Carnegie Mellon University decided to dig in deeper to this common belief — and what they found is surprising. In short, their results showed that couples who doubled the sex they were having were not only less happy, they also wanted sex less and didn't enjoy it as much. "It wasn't the result I expected or hoped for," says George Loewenstein, professor of economics and psychology at Carnegie Mellon University, who was interviewed via email. But does the findings were not also entirely straightforward. Here's what to make of the study.

What We Know about Sex and Happiness
Sex makes us happy, so it would make sense that more sex makes us happier. Multiple studies have found that people generally rate sex as the activity that makes them the happiest of any regular activities. Others have concluded that, at least for men, greater amounts of physical intimacy — including touching, kissing, and cuddling, along with sex — is associated with greater relationship happiness. Still this doesn't tell us which comes first, happiness or sex, or whether they are both reliant on other factors. Loewenstein and his fellow researchers set out to make inroads into this question of directionality. They did so by assigning couples to have more sex, a first as far as Loewenstein knows.

The Study Itself
There were 128 participants in this study, all married couples where both partners were between the ages of 35 and 65. From the beginning, these couples were having sex at least once a month but no more than three times a week to be allowed in the study. The treatment group, which held 70 people was asked to double the amount of sex they were having. Every day the participants were surveyed about their feelings, and asked questions about their libido, the type of sex they were having, how much they liked it, and whether they wanted more.

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The couples in the treatment group did their homework, having 40 percent more sex, on average. Contrary to what we would guess, these couples became less happy. They also wanted sex less and didn't enjoy it as much as the couples in the study who weren't asked to increase their sex sessions.

What the Researchers Thought They Would Find
"I started the research because I know so many older middle age couples who have little or no sex, it seemed unfortunate to me," says Lowenstein. "And I had a theory that, I thought, could explain why." His theory is that this situation is an instance of what he calls hot-cold empathy gaps. This is a biased way of thinking where a person overlooks the influence of their current state on their ability to understand how they would feel in a different state.

Applied to this research, the theory suggests that long-term couples — who might not be as aroused by their partner as they once were — may be unable to understand how having sex would be beneficial. In their "cold" state, they don't accurately imagine how things would differ in their "hot" state. With this theory in mind, Loewenstein was seeing if this study would support his intuition that couples are having as less sex than would be optimal for them.

How This Changed Their Thinking
The results of this study don't support Loewenstein's belief that couples should be having more sex. Neither does it disprove it. "Despite the finding, it would be a mistake to conclude that more sex isn't good for a relationship, for happiness, health and general fulfillment," he says. They can't be sure but the researchers think that the unexpected outcome may have, in part, been due to the fact that the increase in sex was part of an experiment; sex became more work than play.

What the study does suggest is that more sex, in the most basic sense, is not the key to happiness. Instead, Loewenstein says the secret is likely better quality sex, which will likely lead to increased quantity as well. In other words, quit mentally tallying how often you do it and move your focus to enjoying the sex you have.