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Contrary to popular opinion, people who say they are still madly in love with their spouses after more than two decades are not crazy. At least, some of them aren't. And in answer to your next question, apparently they're not lying either. This is the proposition of a new study published in the December issue of Social Cognitive and Affective Neuroscience that took brain scans of long-married people who claimed to still be besotted with their marital partner.

The prevailing theory on romantic love is that it more or less serves the same purpose as the booster rocket in expeditions into outer space. The initial tingly can't-think-about-anything-else swooning launches the couple into orbit, but falls away after the spacecraft reaches a certain altitude, to be replaced by "companionate love," a more regulated, less passionate affection that binds two people together, bolted together a bit with shared history and interests.

Companionate love gets a bit of a bad rap in some corners, since it can feel to some a little too like orbiting outer space: cold, airless and seemingly interminable.

But there are couples who claim more than this, who claim to still be knee-bucklingly in love with their partners, for whom the orbit is not dreary but a wonderful journey with their North Star. One of the theories on these individuals is that they're kidding themselves, or fronting. Another is that they're mentally unhealthy, or generally obsessive.

Bianca Acevedo and Arthur Aron, both at the Psychology Department at Stony Brook University in New York, and their co-authors, decided to investigate. They found 17 people who claim to still be madly in love with their spouses, even after an average of 21 years of marriage. While an fMRI scanned the brain, each partner looked at a picture of his or her beloved.

They compared these brain scans with those of people who have recently fallen in love. In several key ways they looked very similar.

It's already known that newly in love individuals show activity in dopamine-rich areas when they view images of or think about their significant others. This means the Ventral Tegmental Area (VTA), which is part of the reward center, shows a lot of activity. (This is also the area that lights up on the brain scans of addicts when they take cocaine.) And sure enough, in scans of couple still moony after two decades, there it is again.

But, unlike those who are newly in love, the long-in-love brains show no activity among the areas that are commonly associated with anxiety and fear. "Individuals in long-term relationships may experience the excitement, sexual attraction, engagement, and intensity associated with romantic love," says Acevedo. "But they report pining, anxiety, intrusive thinking far less than individuals newly in love."

The brain scans echo this. In fact, they show not just the absence of anxiety, but its opposite. "Interestingly, we found activation of opiate-rich sites, such as the posterior globus pallidus," says Acevedo. "These sites are associated with pleasure and pain relief. They are also activated by primary rewards such as food, and substances such as morphine."

Not surprisingly the scans also show a lot more activation in brain regions that are associated with maternal love, or pairs bonding. This doesn't mean people want to mother their spouses, but just that the attachments formed are similar to those that grow between mothers and their new children.

The study also compared the resulting scans with those of people looking at pictures of good friends and little known acquaintances, to make clear what was the result of fondness and what was the real-soulmate-deal. Pairs bonding is evident there too, but not as strongly.

What are the implications of all this? Well, some of it, warns Aron, the study's co-author, may bum people out. "This is not something long term couples want to hear," he says, about people's undimming passion for their mates. "Nobody wants to hear about couple doing better than they are. We all like to believe we're the best."

The authors recommend that marital therapists do not dismiss romantic love as a possibility and a desirable outcome in a marriage - as opposed to just aiming for conflict -resolution and better communication skills.

Aron's other research has led him to believe the most successful couples are those in which partners help each other expand their ideas of themselves. He also notes the couples who were still in love reported having sex frequently (adjusted for age, natch) although it's not clear whether this is an expression of their undying passion or a cause of it.

Envy about others' more epic love-stories aside, the study is good news for fans of long-term marriage of any type: "Romantic love need not be replaced with companionate love," says Acevedo. "Both can co-exist."