The Gottmans do tend toward sweeping, authoritative statements: They assert, for instance, that 69 percent of relationship problems never get solved. Or that there are four communication styles that can foretell the end of a relationship (criticism, contempt, defensiveness and stonewalling). Those kinds of claims might sound out of place at a research conference, Dr. Whitton said, but she admires the Gottmans’ ability to make their findings accessible to people seeking practical advice.

“I personally use their approaches all the time, not only as a therapist but as a person in relationships,” said Rafaella Smith-Fiallo, a licensed clinical social worker and sex and couples therapist in St. Louis, Mo., who has trained in the Gottman Method. “I find them to be very practical and direct.”

The couple are, in many ways, their own best case study, offering a realistic example of what a thriving long term relationship looks like. During a rough patch early in their marriage, they saw a couples therapist for a handful of sessions, but the counselor clearly preferred John, he said. (“I thought she was a great therapist!” John recalled, smiling.) So they stopped going, and instead turned to their research for guidance.

“We have conflict. We have fights. There are times that we don’t like each other very much,” John said. “But we use these tools, and over time they really have become second nature.”

They turn toward each other “all the time,” Julie said. When John is reading his Kindle and shares something out loud, Julie will stop to listen. If she asks him to clean up something around the house, he says sure. And they are affectionate. During our video interview from their home in Portland, Ore., where they spend time to be closer to their daughter, son-in-law and 8-month-old grandson, Julie gently touched John’s shoulder at least five times.

Like many relationship experts, the Gottmans recommend that couples have regular date nights — it’s a nonnegotiable in their own marriage.

“When we were younger and we didn’t have much money, we would go to a beautiful hotel in Seattle that had a fantastic lobby with a big stone fireplace and soft, beautiful couches. We would claim one and pretend we were guests,” Julie said. “We would order one glass of something, and we would talk for hours, just asking each other big, open-ended questions. We would ask: ‘Is there anything more I can do to show you how much I love you?’”