I first heard about the male deficit model, the sociological theory that men are lousy at friendship, a few months after my friend Matt moved to Seattle.

According to the Male Deficit Model, friendships between men function and falter within strict pragmatic categories: "convenience friends," for example, exchange helpful favors but don't interact much otherwise; "mentor friends," who connect primarily through one man's tutelage of the other; or "activity friends," which Matt and I became by surfing in San Francisco.
 
The theory holds that men tend to drift apart whenever the shared convenience, mentorship, or activity ends. That's precisely what happened to Matt and me when I got married and became a father and no longer had much time to spend in the water. Our friendship only rekindled after Matt and his wife bought a fixer-upper in my neighborhood. I brought over my sledgehammer and Sawzall and we had a blast demolishing the walls of his old kitchen. Then his wife had a baby and we'd push our strollers around the neighborhood.

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Typically, when I got home from hanging with Matt, my wife, Liz, would say something like, "Well, what do you have for me?" Dish, she meant – like maybe some of that marital strife.

My reply almost always was, "Well, umm . . . I don't know."

"Two hours you were gone!" she'd gripe, incredulous. "Think!"

"OK, Matt does want a new seven-footer, mostly for tube riding. Does that count?"

Then Liz would let out a big theatrical groan that said, in essence, What kind of friendship is that?

I thought it was a great friendship, if I thought about it at all. But then Matt's wife, Jodi, accepted a job offer in Seattle. Matt and I told ourselves nothing would change. Jodi and Liz even arranged a surprise "bromantic" (their word) surf trip to Baja that winter. When Liz told me, I had to laugh: It was like Matt and I were little boys, depending on our moms to plan a playdate.

But then, in perfect accordance with the male deficit model, reality set in. First, Matt canceled our farewell beers-and-barbecue session; he was too busy packing. Then, a month after the move, Matt came back to town on a three-day work trip but was too busy to drop by. A month later, he came down for a friend's 50th birthday party, and I saw him for all of 10 minutes – at the party.

Feeling stung and sensing our friendship was toast, I told Liz I was thinking about canceling the Baja trip.

The Male Deficit Model is based on 30 years of research into friendship and relationships — from Mayta Caldwell's and Letitia Peplau's 1982 UCLA study, which found that male friendships are far less intimate than female friendships, to a 2007 study at the College of the Holy Cross in Worcester, Massachusetts, which reported greater interpersonal competition and lower friendship satisfaction among men. A just-completed report from California State University Humboldt, meanwhile, holds that the closer men adhere to traditional male gender roles, like self-reliance and a reluctance to spill their guts, the worse their friendships fare. "Since most men don't let themselves think or feel about friendship, this immense collective and personal disappointment is usually concealed, sloughed over, shrugged away," writes the psychologist Stuart Miller in his opus, Men and Friendship. "The older we get, the more we accept our essential friendlessness."
 
So your social life could be better. Big deal, right? Actually, it's a bigger deal than you might know.

That's because nearly all research into healthy aging has found that the key to a long, happy life is not diet or exercise but strong social connections – that is, friendships. Loneliness accelerates age-related declines in cognition and motor function, while a single good friend has been shown to make as much as a 10-year difference in overall life expectancy. A huge meta-study performed in part at Brigham Young University, which reviewed 148 studies with a combined 308,849 subject participants, found that loneliness is just as harmful to health as not exercising, smoking 15 cigarettes a day, and alcoholism, and fully twice as bad as being obese. Still more startling is a 2010 study published in the Journal of Clinical Oncology that looked at 2,230 cancer patients in China. Social well-being, including friendship, turned out to be the number one predictor of survival.

Some of this stems from the fact that isolated people tend to exercise less, eat poorly, and drink too much. But some researchers believe that loneliness has a negative health impact all on its own. In numerous studies over the past 30 years, John T. Cacioppo, a professor of psychology at the University of Chicago and the pioneer of the biological study of loneliness, has found that lonely people have chronically elevated levels of the stress and fear hormones cortisol and epinephrine. In a 2007 paper published in Genome Biology, Cacioppo even demonstrated a correlation between loneliness and the activity of certain genes associated with systemic inflammation, elevating risk for viral invasion and cardiovascular disease.

And yet the capacity of men to combat loneliness – and improve their health – by building strong friendships seems to be steadily eroding. Cambridge, Massachusetts, professors Jacqueline Olds and Richard S. Schwartz, writing in The Lonely American: Drifting Apart in the Twenty-First Century, point to a current tendency among adults to build stronger, more intimate marriages at the expense of almost all other social connections. In a study of contemporary childcare arrangements, Olds and Schwartz found a deep sense of loneliness among many parents, especially men. "Almost every father we spoke with explained that he had lost contact with most of his male friends," they write. And lest you believe family is company enough, the 2005 Australian Longitudinal Study of Aging showed that family relationships have almost no impact on longevity. Friendships, by contrast, boosted life span as much as 22 percent.

And don't think you're immune because of the great relationship you have with your wife. A team of researchers from around the world analyzed a vast mobile phone database – 2 billion calls and 500 million text messages – and found that by the time married women hit 45 or so, they demote their husbands from first to second place among their most important relationships, typically in favor of a daughter or a younger female friend. It turns out our wives are going to dump us without even leaving the marriage.

To get some perspective, I put the question to my 75-year-old father and three of his buddies. I asked their opinion of the male deficit model and discovered that they thought I had a male deficit all my own, just for entertaining such paleo-feminist horseshit. Two of these guys, Merv and Denis, had no memory of a single friendless year, nor of losing a friend for any reason other than abject betrayal – like the time one guy bedded another guy's live-in girlfriend.

Of course, it wasn't all Butch and Sundance. A public-interest lawyer named Steve described waking up at age 45 and saying, "Hey, what happened to all my friends?" My father escaped that fate only because Denis showed up twice a week at his office, dragging him off to the gym to lift weights.

"I had to go right into your dad's office and just sit and wait," Denis told me. "At 5-of-5 his phone would ring again and I'd yell, 'Don't answer!' "

Several of these men said they continue to meet weekly for lunch. Which brings up a rival theory of male friendship – the alternate paths model. According to this line of thinking, the male deficit model is a historical aberration brought on by two unrelated cultural developments. The first is the rise of contemporary homosexual identity, which had the effect of pushing straight male intimacy into a closet of its own. At the same time, a wave of feminist sociologists and psychologists began describing female friendship, with all its confessional talk, as the optimal model.

Many feminist thinkers now see those views as overly simplistic. And as recent news about gay marriage shows, America is growing more comfortable with homosexuality.

Still others argue that in an era of dual-income households, the very idea of friendship is changing. "Fifty years ago, you wouldn't know the other dads from childcare or school drop-off," says Jon Miller, director of the Longitudinal Survey of American Youth, a vast survey of Generation-X lifestyle habits. "I'm not sure this whole logic that men and women have to have separate friendships makes sense anymore," Miller told me. "Ozzie and Harriet went away. We don't do it that way anymore."

I buy this. I do think I came of age in a uniquely dumb time for male friendship, when we were all so freaked-out about seeming gay that we'd leave an empty seat between us at the movies. I'm also open to Miller's idea that social life is changing, and not necessarily for the worse.

But I think men really do suck at friendship. So I decided to make a conscious effort to fix things with Matt. Not that I did a great job. My way of telling him I was angry was to ignore a couple of his emails. Then I ignored a couple of his voice mails. Finally, when I did answer the phone, he said, "Dude, are you boycotting me?"

"No. Why?" (Go ahead, judge me. It worked.)

"Come on, man. I can't take it," he said. "You're, like, my best friend."

"Look," I said, "you are my best friend. So I'm hurt! I mean, two weekends and no coffee? No beer?"

Matt apologized and said he felt terrible about the whole thing. And just like that, our friendship was back on track. Christmas came, and Jodi surprised Matt with the Baja trip. He was psyched, and I decided to go for it, too. The surf wasn't all-time, but it was shoulder-high and plenty of fun. In the evenings, we'd retire to a little desert town for dinner and beers. We chattered about waves and kids. It felt great and energizing.

But then Matt flew back to Seattle and I flew back to San Francisco and we settled back into pretty much never calling each other, and I found myself in the same place I was when he moved, with my wife as my sole, genuine confidante. But this time, I decided to get proactive. I started with an old climbing buddy and two people I knew through married-couple get-togethers. To all three, and mostly through a lack of imagination, I suggested dinner minus the wives. All three said more or less the same thing — "Hell yes, when?" — which confirmed that I wasn't the only middle-aged guy looking for a buddy. In all three cases, the pattern was the same: first, a few pleasant meals together, followed by a sense that dinner wasn't exactly our proper form, and then the acknowledgment that we needed an activity. But that hardly adds up to a male deficit.
 
I solved the problem easily enough with the dinner-party husbands by inviting them over a little before the wives and kids, so we could shoot the breeze while cooking a meat-centric meal together. My old climbing partner and I began trading emails about adventures we could have together. He voted for a big alpine climb; I proposed a triathlon; and we settled on cycling. We agreed on a 100-mile race a couple months away, signing up online. He sent me an email saying, "Might as well bang out some training rides together, huh? Just to beat the boredom?"
 
One morning, I got home from a long training ride with him just as Liz returned from dropping the kids at school. She said, "How was biking, honey?"

"Awesome. Gorgeous morning."

"What do you got for me? Any dish?"

"Ummm . . ."

"Oh, God," she said. "Forget I asked."