We live in a universe that conforms to what one might call reductionistic analysis: the behavior of the macroscale objects that we see around us (objects like people) can be explained by regarding those objects as conglomerates of simple building blocks called elementary particles which obey the same physical laws whether they are part of a machine gun or part of a dopamine receptor in your brain.

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 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. 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.

Keeping the Fires Burning - research has found that passionate, long-lasting relationships generally have several things in common:

• The couple is not facing terrible "external stressors," such as war or the loss of a child.
• One partner is not highly depressed or anxious.
• Both know how to communicate with each other.
• The couple does new, challenging things together.
• When one partner is successful, the other celebrates the success.