Then, in May 2015, came a breakthrough. Before a game of pool at Amsterdam Billiards, they stopped for dinner at Porteno in Chelsea. Dr. Fisher pulled a cocktail napkin out from under her glass at the restaurant and said, “Why don’t we write down what we’d secretly like if we win at pool?” She wrote “a real kiss.” He wrote “sex and clarity.” He won.
As he walked her home that night, she said, “I do study love. When you start to make love with someone, you contribute to the brain circuitry for attachment. Are you willing to take that chance?” Mr. Tierney said he was. By November, though, he was worried their relationship was getting too serious. He broke up with her in Grand Central Terminal.
“I was just numb,” she said. “I cried.”
But then, on New Year’s Eve, came an email from Mr. Tierney. He told Dr. Fisher she was the best thing that had happened to him that year. Two weeks later they were dating again, without a commitment, until his son, Luke, left for college in the fall of 2017. Then they worked out an arrangement that still holds.
“I said, I’ll marry you, but I’m not moving in,” she said. She maintains her apartment near Central Park, and he lives in the Spuyten Duyvil neighborhood of the Bronx, where he proposed on July 2. Two nights a week, they say good night over the phone. “I miss him terribly, but it’s a great way to have a really long-term romance.”
On July 21, at the ranch near Red Lodge, Mont., where both first experienced the mutual dopamine rush, they eloped. Mr. Ohrstrom, a New York investor and philanthropist, officiated wearing a king of hearts costume.
Dr. Fisher said her relationship with Mr. Tierney is one she has enjoyed “living, not dissecting.” And Mr. Tierney knows he’s in good hands, relationship-wise. “At first I did wonder about the wisdom of dating the world’s most-quoted authority on love, but I quickly discovered it was a blessing,” he said. “Helen doesn’t play games. She knows what she’s doing.”