Former Vice President Al Gore and his wife Tipper never showed public signs of a disintegrating relationship, so for many, the couple's announcement that they are separating after 40 years of marriage comes as a surprise.
"I'm shocked -- beyond shocked," family friend Chris Downey told the Washington Post on Tuesday, as pundits and journalists reminisced about the couple's moments in the public eye.
Though every marriage is different, a divorce after 40 years is "unusual," said Robert Levenson, a psychologist at the University of California, Berkeley, who studies marriage across the lifespan. Most divorces occur early in marriage, Levenson said.
"It's striking when a couple has been together 40 years and then they call it quits," Levenson told LiveScience. "It's not what we would expect."
Marriages get in trouble when the couple's situation or relationship changes and the partners can't adapt, Levenson said. The birth of the first child is particularly fraught, he said. Tensions over housekeeping, finances and childrearing can run high. A 2000 study published in the Journal of Marriage and the Family by Levenson and psychologist John Gottman, now at the Gottman Relationship Institute, found that divorces during this period tended to be marked by anger and vicious fights.
As couples overcome challenges together, however, relationships strengthen. People report more marital satisfaction in midlife, with a bump in bliss as the children grow up and leave home, Levenson said.
"A lot of couples rediscover each other," Levenson said.
In fact, said Terri Orbuch, a University of Michigan psychologist and author of "5 Simple Steps to Take Your Marriage from Good to Great" (Random House 2009), people are often happier by their 35th anniversary than they were when they first got married.
According to friends of the couple, the Gores cited "growing apart" as the reason for their split. That's a common reason for midlife divorces, Orbuch said. Relationship ruts and boredom are common. Spouses forget to show appreciation for each other, leading to frustration and loneliness. Orbuch's research has shown that marriages with husbands who don't feel appreciated are twice as likely to end. Divorces in this phase of life are often marked by coldness and emotional withdrawal, according to Gottman and Levenson's 2000 study.
"Things can start out small and seemingly insignificant," Orbuch said. "What happens is they accumulate over time and they become bigger and bigger."
Couples can overcome these challenges by communicating, learning to fight fair, and discussing each other's expectations for the relationship. To overcome ennui, Orbuch said, both parties should focus on adding spice to the relationship, which can be as simple as a new restaurant or vacation spot.
"Happy couples that are still together over time change things up," she said. "They knock each other off balance just a little bit."
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.