MELVILLE, N.Y. — Suzanne Bernstein said she and her husband, Sidney, eat side-by-side when they go out, always walk hand-in-hand, and begin and end each day with "I love you."

The couple from Weehawken, N.J., have been married 18 years and Suzanne said the relationship is as passionate as when they first met.

Now research exists to support her claim.

Stony Brook University researchers looked at the brains of Bernstein and 16 other people who had been married an average of 20 years and claimed to be still intensely in love. They found that their MRIs showed activity in the same regions of the brain as those who had just fallen in love.

"It's always been assumed that passionate love inevitably declines over time," said Arthur Aron, a social psychologist at New York's Stony Brook University and one of four authors of the study, presented in November at the Society for Neuroscience annual meeting in Washington, D.C.

"But in survey after survey we always have these people who have been together a long time and say they are intensely in love. It was always chalked up to self-deception or trying to make a good impression," he said.

This study suggests that's not the case, said Bianca Acevedo. Acevedo, now a postdoctoral student at Albert Einstein College of Medicine in the Bronx, is the chief author of the study she conducted for her doctoral dissertation in psychology, working under Aron while she was at Stony Brook.

In fact, she said, the study found an advantage to the longer-term relationships she studied: The brains of those people showed less anxiety and obsessiveness.

Aron had conducted an earlier MRI study published in 2005 among 17 people who had recently fallen in love. He found that regions of the brain associated generally with reward and motivation — the same regions that light up when cocaine is taken — activated when the subjects were shown pictures of their beloved. These regions, Aron said, are not the same as those associated with sexual arousal.

Using the same approach, the researchers recruited 17 people who, like Bernstein, said they were still madly in love with their spouses. Bernstein, 59, a retired teacher, said she learned of Acevedo's research from a newspaper story and contacted her at Stony Brook. "It dawned on me that the article pertained to myself," she said.

Acevedo said it was impossible to extrapolate from their study what percentage of long-lasting couples might register the same intensity of emotion as her 17 subjects. But she said a previous phone survey of several hundred people in long-term relationships she and Aron conducted found about 35 percent rated their feeling for their partners as very intense. "We were shocked," she said. "We hadn't predicted it would be that high."