The stranger struck up conversation on a delayed flight between Florida and New York. We were both struggling to entertain our toddlers, and we commiserated awhile. After the children fell asleep, he told me he’d recently left the Mormon church. He said he missed the community and the certainty he once felt. He was still figuring out how to raise a child without faith: for example, would I say there was a heaven if my daughter asked, even if I didn’t fully believe it?

Maybe it feels more natural to speak intimately with a stranger on a flight, when you are both uprooted and disoriented, not quite sure if it’s night or day or where the sun should hang in the sky. Maybe it’s more natural for your mind to turn to existential questions when you’re hurtling through the atmosphere at great speed, held up by forces you can’t fully understand. For a few hours we talked about fear and loss, and I later thought that while this kind of intensity is discouraged, maybe such subjects are actually best explored with someone completely unfamiliar to you, who sees the world quite differently.

Once on solid ground again, the man told me he’d actually had a lot of life-changing chats with strangers. He was inspired by the cognitive scientist Laurie Santos, whose course on the science of wellbeing, the most popular in Yale’s 300-year history, is now available for free online. Santos teaches that the pursuit of happiness is often counterintuitive. The things we think will make us feel happier – acing exams, securing a dream job, buying that dress – usually don’t, but small habits can make a big difference. One of them is talking to strangers.

While we tend to focus on our close relationships, psychologists have noticed that even what they call “minimal social interactions” can make us feel happier and more connected. One study found that people who had a brief chat with their barista, or simply made eye contact and smiled, felt happier and experienced a greater sense of belonging than those who treated the human being in front of them as an extension of the coffee machine. A 2014 paper poignantly titled “Mistakenly seeking solitude” found that people who were instructed to talk to fellow passengers on Chicago public transport felt more positive about their commute than those who didn’t.

The researchers observed that we consistently underestimate how much we will enjoy speaking to a stranger, and how much a stranger will enjoy speaking to us – which they demonstrated when they, somewhat remarkably, replicated their Chicago findings with commuters in London. We assume that among strangers it’s best to stick to small talk, but when people in studies are instructed to go deep with someone they don’t know, they surprise themselves with how enjoyable – and unawkward – it is.

And yet modern life is organised to reduce these encounters. It has become easy to avoid speaking to anyone unfamiliar. You can work from home or commute with your headphones in and eyes fixed to a screen; you can use the self-checkout or order almost anything via an app. We’re herd creatures who have become antisocial. With our smartphones in hand, we’re forever reachable and yet perpetually remote from one another, distracted by our devices.

We tend to approach strangers differently now: the internet has made it cheap and effortless to speak to new people in far-flung places, or to speak to hundreds of strangers at once, and it has helped those who would have otherwise felt desperately isolated find their tribe. But there’s a cost to building a community remotely while you live among total strangers. One charity survey found that one in five people have never spoken to their neighbours, and one in five say there is no one in their neighbourhood, beyond their immediate family, they could call on for support.

Because we don’t properly value minimal social interactions, we aren’t fully recognising what it means to lose them. But I think we feel it. One recent survey suggested that 7% of people in Great Britain report chronic loneliness. Another report found the same proportion say they don’t have a single close friend. It’s a predictable consequence of the erosion of community spaces, the closure of libraries, community centres and pubs, but it also suggests that despite our online hyper-connectedness, many people are struggling to build social bonds that feel meaningful.

When people talk to more strangers, this isn’t only good for them as individuals, it’s good for society at large. Studies show that an effective way to combat prejudice is to bring people together and get them talking: it is easier to demonise difference from a distance. For all the panic about online echo chambers and filter bubbles, the evidence suggests that our biggest echo chambers still exist in our offline lives: we tend to only hang out with people who see the world similarly to us. And yet the internet is not the best place to meet strangers who might alter your perspective or change your mind. Not only do algorithmic feeds expose us to polarising extremes, but we seem to react with greater hostility to people we disagree with when we interact with them online rather than in person. Researchers have found, for instance, that people are more likely to dehumanise someone they disagree with politically when they read their opponent’s views than when they hear them talk. In other words, in a divided world, one kind thing we can do for one another is find new ways to talk, in real life.

I feel lucky that as a journalist I speak to more strangers than most. These include people who have moved or surprised me, taught me something new or made me see life differently. But when pressed, most of us can identify a cast of strangers who have touched our lives in profound or intangible ways.

Encounters with strangers can be a humbling reminder of the vastness of the world and of each other, the impossible-feeling truth that each one of us contains an entire universe of inner life and a singular perspective, that as a species we have an incredible capacity for kindness, cruelty, courage and creativity.

Further reading

The Power of Strangers by Joe Keohane (Penguin, £10.99)

Letter to a Stranger: Essays to the Ones That Haunt Us by Colleen Kinder (Algonquin, £15.99)

The Hope Circuit by Martin Seligman (John Murray, £16.99)