It’s 7am on a Monday and my heart is racing. Normally my Mondays are reserved for tedious activities, but this morning I’m chasing a high. I’m not in a nightclub greeting sunrise with a tequila, sadly, but in an east London café. The source of my palpitations? I’m steeling myself to strike up a conversation with an unsuspecting man a few tables away.

Given that I’m a journalist who interviews people for a living, you might think I’m being overly dramatic. But talking to strangers can be terrifying. The unpredictability of how they will respond to your overture, and the possibility of rejection, is paralysing. Perhaps the worst fear of all: might they find me annoying?

I eventually find my resolve, turn and squeak: “Is this your local spot?” You’ll be pleased to hear that a lively conversation ensues – dyslexia and sourdough bread are discussed – and afterwards I experience a small buzz.

Conversations with strangers can be exhilarating. Joe Keohane, a journalist and author of The Power of Strangers, tells me my high could be attributable to a sense of “relief” that an uncertain situation has panned out well. A professor he interviewed for his book linked it to oxytocin, a chemical released in our brains when we bond with others.

Yet strangers offer more than a temporary boost: Keohane is convinced that many of our gravest ills, both on an individual and societal scale, can only be cured by engaging with people we don’t know. We rarely interact with folks who don’t share our views – except to cancel them on Twitter. But in a world riven with political, social and racial divides, speaking with strangers opens windows to other minds. It can deepen empathy by prompting us to see those around us as fully formed individuals rather than cardboard cut-outs. And it can alleviate loneliness.

“I can’t think of a way out of a lot of these problems that doesn’t involve figuring out how to talk to each other,” Keohane says, speaking over Zoom from his Brooklyn office.

He’s fighting an uphill battle. Conversations with strangers have gone the way of the dodo in our busy modern lives. When in public I only have eyes for my iPhone and my ears are clogged with headphones. Technology has erased the need for unplanned encounters – awkward, meaningful or otherwise. By introducing masks, social distancing and the notion that strangers make us sick, the pandemic added yet another layer of bubble wrap between us and the outside.

I’m puncturing that by undertaking a two-week experiment in which I interact with as many strangers as possible. The assignment made me gulp: Londoners are hardly known for their warmth (the capital was once judged the world’s second-least-friendly city, after Paris).

But as the city reopens, there’s a certain bonhomie in the air. Taking cues from Keohane, I ignite chatter in supermarkets, shops and restaurants. I join a running club. I tag along with an activist for a “Free Listening” session (based on a Californian movement) in which we stand in a park with a sign and wait for people to approach. I natter with homeless people, elevator companions and waitstaff – but stop short of accosting pedestrians in the street. The point is not to be a public nuisance, but to see what happens when I simply remove the blinkers and am open to interacting with unfamiliar faces.

Strangers represent a vast reservoir of colour, comfort and intrigue. They can surprise us in ways our friends cannot. But speaking to them means reintroducing friction – an uncomfortable moment here, a detour there – into our lives. Although we’re out of practice, we are “ultra-social apes” by nature, as evolutionary psychologist Michael Tomasello says, and our skills will sharpen quickly if we put in the work. Potentially life-changing payoffs await, but are we willing to yank ourselves off autopilot?

“The need to speak to strangers is greater now than it has been in a very long time,” Keohane says. Although we’ve been retreating from the physical world since the turn of the millennium, the pandemic dialled up our insularity and “showed us the logical conclusion of that trajectory: everything is done on the internet and there’s a total cessation of contact,” he says. “You get everything delivered, never leave your house and never mingle.”

Now, as restrictions lift, he says we have the opportunity to reflect by asking ourselves: “Did we enjoy living like this? Do we feel our social needs were met?” As soaring rates of loneliness, depression and anxiety during 2020 can attest (according to one US survey, symptoms of anxiety or depression were up by 31% from 2019), for many the answer will be a definitive “No”.

Keohane’s concern for this subject predates the pandemic. A former Esquire editor who grew up in Boston (“a very talky place”), he’s an affable 44-year-old with a tanned, open face. But a few years ago, in an all-too-familiar scenario, he realised he had stopped talking to people. “When I went to bars, I would sit and look at Twitter because it was easy,” he says. “I started feeling weird about it: like an element of serendipity had been removed from my life because I had obliterated an entire category of interaction.”

That sent him down a corrective path. Over the next two or so years he attended listening workshops, consulted academics and interviewed activists; he chatted to people in trains, bars and libraries from the UK to Mexico. “I resolved to start speaking to strangers again, but also to understand why I had stopped and why other people are so hesitant to do it,” he says. “I wanted to take something that seems like a relatively simple interaction and really pry it apart.”

It may seem simple, but talking to strangers is a dance like no other. Irrespective of whether you’re extroverted or introverted, it requires considerably more effort than gabbing with a friend. “You have no frame of reference for this person so you really have to listen and watch their body language, while also thinking about your response,” Keohane says. “It’s a very complex interaction on a lot of levels.”

Oscar Ybarra, a psychologist at the University of Michigan, , says speaking with strangers is a form of “mental exercise” that can improve our cognitive functioning. The more we do it, the better we perform. But those muscles have atrophied – especially for younger generations. “Research shows college students have a really hard time meeting new people,” says Keohane. “Most of their communications have moved online or on to phones, where you can control the conversation: you can take all the time you want to respond. This is the first time in history where you don’t have to respond immediately to someone who’s saying something to you. As a result, there’s a serious erosion of social skills among young people.”

It’s perhaps unsurprising, then, that youths suffer from higher rates of loneliness compared to other demographics. According to a 2019 YouGov survey, a staggering 88% of Brits aged 18-24 experience loneliness to some degree (compared to 70% of those aged over-55). While strangers won’t fix this entirely – they’re not a stand-in for primary relationships – they can make us “feel connected and alleviate feelings of estrangement and isolation,” Keohane says.

This filters into politics. Noreena Hertz, the author of The Lonely Century (2021), is the latest academic to link isolation to populism: she found that loneliness connects far-right-wing voters in the UK, France and the US. “A lot of the hardcore conspiracy-mongering and extremism we’re seeing can be tied to people feeling that they’re not being listened to,” Keohane says.

One of the most compelling passages in The Power of Strangers focuses on Theodore Zeldin, an 87-year-old Oxford professor who hosts events called the Feast of Strangers and is on a mission to meet as many people as possible. Zeldin refers to himself as an “explorer” who has spent his life “discovering the world, one [person] by one.” He has previously stated that he enjoys speaking to people who do not share his viewpoint: “I would argue that finding something admirable, or touching, in an obnoxious person, is also profoundly satisfying.”

The idea of chatterboxes as explorers prospecting for lively conversations stuck with me – as did the thought of relishing interactions with people with whom we seemingly have nothing in common. The internet and social media may have exposed us to more strangers than ever, as Keohane notes, but it’s easy to dismiss and dehumanise people when they’re avatars on a screen. When they’re standing in front of you, it’s far more difficult.

Keohane describes Zeldin’s escapades as a “great humanitarian mission.” By learning about thousands of different people, “he’s eliminating the luxury of easy answers and pat explanations”. Keohane thinks a deeper understanding of others, of their backstories and tics, “can help heal an ailing democracy, which is what we have here and what you have [in the UK] at the moment, too.”

I’m all for saving democracy but, as I stand in the supermarket queue mustering the courage to start a conversation with literally anyone, all I can think is: why would this person want to talk to me? By obscuring facial expressions, masks only make the prospect more daunting.

Fear of rejection is a crippling and common thought, but Keohane says people are friendlier – or more polite – than we think. A 2019 study in which hundreds of participants in Chicago and London approached strangers, resulted in zero rejections. Even on London trains – ground zero in frostiness – there were, shockingly, no rebuffs.

A greater obstacle to initiating chitchat might be the fact that talking to strangers creates drag. It takes up time and forces us to be present. Given that technology has smoothed out daily wrinkles – ordering online rather than calling the pizza place; using self-service checkouts; swiping through Tinder instead of asking people out face-to-face – it is at odds with modern lives.

Want to start chatting to strangers? Pocket your headphones and go for a walk. “Just notice people,” Keohane says. “See what they’re wearing, how they’re moving. Root yourself in the world.” Try to make eye contact and, if they return your gaze, smile. But don’t stare; there’s a fine line between friendly and Freddy Krueger.

In two weeks, I can count on one hand the number of pedestrians who made eye contact. But the mere act of noticing others – a man unpacking pastries, a woman resembling her whippet – was surprisingly satisfying. And security guards became reliable sources of grins.

It needn’t be an hour-long heart-to-heart in order for an interaction to be beneficial. Gillian Sandstrom, a psychologist at the University of Essex, has concluded that even fleeting interactions can make us feel more connected to our surrounds. She’s right: time and again, my buzz returned. When it seemed like someone might be up for a chat, rather than opting for the standard “How are you?” I commented on their sneakers or book. If they asked how I was, I replied honestly: hungover, stressed, happy. I tweaked the script ever so slightly, as Keohane suggested, to prevent people from cruising through our conversation unblinkingly. It often worked.

Things strangers told me in the past two weeks: the helix is the most painful part of the ear to pierce; Imran Khan, the Pakistani prime minister and ex-cricket star, is an honest man; One Piece, about a boy who wants to become king of the pirates, is the best anime show; there is a hidden courtyard around the corner from my flat; people are mostly kind to disabled people; English-language newspaper coverage of Brazil under Bolsonaro’s reign is lazy; many teachers at London art colleges wear Australia’s Blundstone work-boots; there is a flash sale for a cool Japanese hiking brand a few streets away; I should move to Birmingham; Filipino people are friendly; Auckland is a hidden paradise; Forbidden Nights is a male-stripper revue that absolutely should be on my radar; “organic intelligence” is an up-and-coming form of trauma therapy; a coffee machine is the most expensive thing in a café.

Some of this information is useful, some enlightening, some questionable. A handful of friendships may sprout from these encounters. Even being alerted to the possibility that you’re allowed to talk to other people feels liberating. Without getting too Pollyanna-ish about it, London feels less impenetrable. If I want one of the city’s 9 million strangers to become less strange, I can make it happen; I don’t need to wait to be introduced. I’m aiming for one decent chat every couple of days.

I ask Keohane about his most memorable stranger interaction and he tells me about a homeless woman – a young artist – who lives on 42nd Street and Fifth Avenue in Manhattan. “I consider that a perfect stretch of urban life: there’s the main branch of the New York Public Library, which is a spectacular building, and behind it is Bryant Park, which is gorgeous. There’s a diner a block away where I have lunch, there’s a coffee place I go to. It’s great,” Keohane says. But she sees this patch differently. One morning, a man dragged her into Bryant Park and tried to sexually assault her; his efforts were foiled by a doorman from a nearby hotel who tackled him to the ground. Strangers hurt and saved her.

“What I think is a perfect place is nightmarish for somebody else,” says Keohane. “It’s unlocked a whole new dimension of experience I was blind to before. Now I have a much more complicated perception – and I gained access to it because one day I started talking to her.”

Therein lies the true power of strangers. They can make our lives happier, knottier and more colourful. But most of all, they force us to open our eyes.

The Power of Strangers: The Benefits of Connecting in a Suspicious World by Joe Keohane is published by Penguin at 16.99. Buy it at guardianbookshop.com for £14.78