Peter Lovenheim is the author of “In the Neighborhood: The Search for Community on an American Street, One Sleepover at a Time.” He lives in Rochester, N.Y.

Do you know your neighbors well enough to realize whether something horrible is happening in the house down the street? To call them if you need help? To trust that they’d put themselves at risk to help you?

These were some of the first questions that came to my mind this past week as I watched — riveted, appalled and relieved — the unfolding story of three women rescued after a decade of captivity in a Cleveland house. Those who helped free Amanda Berry and her 6-year-old daughter, leading to the discovery of the two other women, weren’t police officers or detectives who’d been on the case for years. They were two neighbors: Charles Ramsey and Angel Cordero.

Ramsey, apparently, had occasionally shared words and barbecue with the alleged kidnapper, Ariel Castro, before he saw Berry screaming for help at the door and answered her calls. Other neighbors are stating that they saw unusual, troubling things at the Castro house over the years — porch lights left on, a child at an attic window, even a woman crawling naked in the back yard. They say they called police, but police say they have no records of the calls.

The fault of this horrible crime, of course, is with whoever kidnapped and held these women. But I wonder what would have happened if the neighbors had spoken to one another more and shared their worries. I wonder if, collectively, they would have pushed law enforcement authorities to check things out, to get involved. I wonder if this tragedy could have been discovered much sooner if the neighbors on Seymour Avenue had been, well, a little more neighborly.

The upper-floor window of the Cleveland home where Amanda Berry, Gina DeJesus and Michelle Knight were held captive for years. (David Duprey/Associated Press)

Whether in high-rise apartment buildings or homes in the suburbs, Americans are growing more distant from their neighbors. In the 2008 General Social Survey, 30 percent of respondents said they spent a social evening with neighbors more than once a month, compared with 44 percent in 1974.

There are exceptions, of course. In my travels around the country to speak about our relationships with those living around us, I’ve found in every community at least some neighborhoods where people know one another, talk regularly and watch out for each other. But these are exceptions — and have been for some time. As Robert Putnam wrote in his 2000 book, “Bowling Alone,” friendly contacts between American neighbors are “measurably more feeble now than a generation ago.”

Sociologists offer various reasons for such side-by-side isolation. The rise in two-career couples means that fewer people are home during the day. We spend more time watching television and using the Internet. In the suburbs, lot and house sizes have nearly doubled since the 1950s, increasing the distance between neighbors. At one time, putting up a fence in the back yard was considered a somewhat hostile act, but today new homes often come with fences already built.

Then there is the pervasive fear of strangers. It used to be that a stranger was just someone we had not yet met; today, a stranger is someone who poses a threat. We’ve gotten to the point where anxiety is the default setting, where it’s acceptable to live side by side, driveway to driveway, with other people for years — decades, even — without knowing each other.

I hadn’t thought much about how we live as neighbors until a tragedy occurred about a decade ago on my suburban street in Rochester, N.Y. A family had lived about 10 houses down for seven years. One night, the husband came home and shot and killed his wife, then himself. The children, an 11-year-old boy and a 12-year-old girl, ran screaming into the night.

I didn’t know the family well, and in asking around, I found that no one else did, either. Much like in Cleveland, there had been some warning signs that became much brighter in hindsight: A few weeks earlier, a neighbor saw a police car in the driveway; a close friend suspected that the husband had purchased a rifle; another neighbor thought the husband’s behavior had recently seemed “off.” But everyone kept their bits of information to themselves, and on the night of the shooting, we were all shocked.

I wondered: Did I live in a true neighborhood or just on a street surrounded by people whose lives were entirely separate from my own? What would it take to get to know the people on my street beyond a casual wave while walking the dog or a passing conversation about newly planted roses?

I recalled sleepovers at friends’ houses when I was a child and how those experiences had given me a sense of what life was like in other people’s homes. It was a bit un­or­tho­dox, but I wondered: Would my neighbors let me sleep over and write about their lives? As it turned out, about half the people I approached said yes. Even the ones who didn’t — citing a reasonable concern for privacy — expressed a similar desire to be better connected to their neighbors.

I asked to sleep over not to compare my neighbors’ sofa beds but to spend time with them and see what a normal day in their houses was like. With their permission, I watched them help their children with their homework, tagged along on a weekday morning to see where they worked, met them at the supermarket when they did their shopping, dropped by the gym when they worked out, sat with them at church or synagogue. I learned that most of us want more or less the same thing — to live among others with a sense of common humanity — and that, at times, there is just no substitute for a neighbor close at hand.

If we live as strangers to one another, we lose the chance to realize that the elderly woman who lives alone in the apartment down the hall has let her newspapers pile up for a week — and maybe someone should check on her. That if three of us on different nights heard angry shouts from the house at the corner, maybe someone should call to see if everything’s okay. That a man down the block, who hardly ever works on his lawn, had his garage door open and bags of nitrogen fertilizer piled high. That the man who lives across the street doesn’t have children, yet there was a young girl at the attic window.

This isn’t about being snoops or invading anyone’s privacy. It’s about looking out for one another.

Every neighborhood is different, and often our busy lives leave us with little energy to reach out. But doing so keeps us safer. Neighbors, too, can enrich our lives in ways we can’t know until we know them.

Neighbors around the country have found inventive ways to meet and connect with one another. Some neighborhoods have gotten people talking to each other by creating directories or maps with residents’ contact information, which can be especially helpful to newcomers. For years, residents in Old Oaks, east of downtown Columbus, Ohio, have been taking turns hosting weekly social hours, called Wednesdays on the Porch, where people come just to chat. In an interview, one resident told me, “My family and friends are consistently amazed that I know my neighbors, they know me, and we have an involvement in each others’ lives that goes beyond fences.”

Annual neighborhood picnics are nice but generally don’t get much traction. But more frequent events — such as a Fourth of July bike parade for kids, maybe with a town fire truck in the lead; a Labor Day back-to-school barbecue; Christmas caroling; or a progressive dinner on New Year’s Eve — can help foster lasting connections.

In Shore Acres, a mixed-income Cleveland neighborhood about 11 miles from Ariel Castro’s house, residents created beauty out of the recent housing bust. When an abandoned house burned down, they arranged for the property to be transferred to the neighborhood association and converted it into a community garden. Similarly, owners of six adjoining rowhouses in Albany, N.Y., took down the fences between their tiny back yards and merged their gardens. Stone footpaths now allow the residents to walk among the plants, shrubs and flowers and spend time with one another. Other neighborhoods have converted empty lots into pocket parks or dog runs.

And some have found that shifting traditional backyard activities to their front yards — such as planting flowers or vegetable gardens — makes neighbors more likely to stop and say hello. A woman who planted a flower garden in her front yard in Philadelphia wrote to me: “Neighbors I knew only by sight now see me outside and stop by to chat. Make yourself available and you will be surprised what doors — and hearts — will open.”

In this age of cheap long-distance phone calls, discount airlines and the Internet, when we can create community anywhere, people sometimes wonder if neighborhoods still matter. I believe they do. Indeed, Charles Ramsey and Angel Cordero remind us of that. They are exceptions to the rule that neighbors mostly keep to themselves. By their intervening, we see that if more neighbors take an interest in each other and watch out for each other, our neighborhoods will be safer and stronger.

Ringing the bell and introducing yourself to an elderly person living alone in your apartment building or inviting a few people on your block over for drinks or dinner is a great place to start.

Read more from Outlook, friend us on Facebook, and follow us on Twitter.