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Why a stranger's hello can do more than just brighten your day

Laura Gao for NPR

Before Gillian Sandstrom became a psychologist, she was a computer programmer. Then she decided to change tracks and pursue a degree in psychology at Toronto Metropolitan University. And she felt like she didn't fit in.

"I was 10 years older than my fellow students," Sandstrom recalls. "I wasn't sure I was meant to be there. I didn't instantly feel like a part of that community."

Enter the hot dog lady.

On her daily walk from one university building to another, Sandstrom would pass a hot dog stand.

"I never bought a hot dog, but every time I walked past, I would smile and wave at her and she'd smile and wave at me," she says.

Sandstrom remembers looking forward to this daily interaction. This brief exchange with a stranger made her feel less isolated.

"She made me feel happy," she says. "I felt better after seeing her and worse if she wasn't there."

Years later, that type of brief but happy encounter inspired Sandstrom to design a study that looks at the benefits of social connections — encounters, even brief ones, with strangers, acquaintances and anyone outside our close circle of family, friends and colleagues.

"This relationship I had with her really got me thinking about how we have so many people in our lives," says Sandstrom, who now works at the University of Sussex. "We're only close to a small number of them, but all of the other people seem to matter a lot and maybe a lot more than we realize."

Her work is part of a growing body of research that looks at the value of social connectedness, not just to our happiness and well-being but our overall physical health. (In fact, social isolation hurts our minds and bodies so much that it's known to increase risk of premature death.)

While much of the research on social connections has focused on the closest relationships in people's lives, Sandstrom and other scientists are now learning that even the most casual contacts with strangers and acquaintances can be tremendously beneficial to our mental health.

Clicking to count contacts

In a 2014 study, Sandstrom tried to find out if the kind of boost she got from her hot dog lady encounters held true for others. She and her colleagues recruited more than 50 participants and gave each of them two clicker counters.

"I asked them to count every time they talked to someone during the day," she explains.

With one clicker they counted their interactions with people they were close to — the kind of social connections sociologists call "strong ties."

The second clicker was for counting so-called "weak ties" — strangers, acquaintances, colleagues we don't often work with.

At the end of each of the six days of the experiment, the participants took an online survey to report how many strong and weak ties they had tallied each day — and how they were feeling.

"In general, people who tended to have more conversations with weak ties tended to be a little happier than people who had fewer of those kinds of interactions on a day-to-day basis," she says.

And each participant was happier on the days they had more of these interactions, she adds.

In a later study, she and her colleagues looked at the impact that talking to strangers has on mood. They recruited 60 people outside a Starbucks in Vancouver, Canada, and gave each of them a gift card. Individuals were randomly assigned to either be as efficient as possible when placing their order — no small talk with the staff — or to be more social with the barista.

"So try to make eye contact, smile, have a little chat, try to make it a genuine social interaction," Sandstrom told them.

When the study participants came back outside, they were sent to a different researcher who didn't know the instructions given to each participant. The researcher then had the participants fill out a questionnaire about their current mood and how much they had interacted with the barista.

It turns out that the people who chatted with the barista were in a better mood and felt a greater sense of belonging than those who didn't interact much with the staff.

"I think lots of people, if they think about it, can tell a story like that about a time where someone that they didn't know at all or didn't know well just really made a difference by listening or smiling or saying a couple of words," says Sandstrom.

Why it matters who you talk to each day

Other research shows that it's not just talking to strangers and acquaintances that makes us happy, but the entire suite of our daily interactions with both weak and strong ties.

Hanne Collins, a graduate student at Harvard Business School, is the lead author of a study on this topic, drawing on data from eight countries. She and her colleagues found that the richer the mix of different relationships in people's daily conversations, the happier and more satisfied they felt. For example, someone who talks to lots of different kinds of people — strangers, acquaintances, friends, family, colleagues — in a day is likely to feel happier than someone who talks only to, say, colleagues and friends.

Having conversations with "lots of different people might build the sense of community and belonging to a larger social structure," says Collins. "That might be very powerful."

Plenty of people will testify to the strength they gain from having a richer mix of people and social interactions in their lives. Their interactions might serve as a guide for those who don't typically engage in conversations with lots of folks — and who may fall into the cohort of people suffering from what the U.S. Surgeon General categorizes as "social isolation."

People in Uganda are always catching up with each other, even their most casual contacts, says Agnes Igoye in Kampala. "It's considered bad manners for someone walking past [anyone] without a greeting," she says. And those greetings often lead to lengthy conversations, she adds.

One such interaction she looks forward to is with a fishmonger who rides his bicycle to her neighborhood to sell fresh fish. She doesn't see him often because she travels a lot for work. But when she does run into him, their conversations are wide-ranging — from gardening advice to updates on his kids.

"I have an avocado tree," Igoye says. The fishmonger has been warning her about the weeds growing around the tree. "The other day he was telling me, 'Oh you need to cut it. It's going to spoil the avocado.' "

As an advocate against human trafficking, Igoye often appears on Ugandan television. People who have seen her on TV often stop to greet her in public spaces. She enjoys the encounters even if she's never met the person before, she says: "It makes me feel good."

In Lagos, Nigeria, psychiatrist Dr. Maymunah Yusuf Kadiri is particularly aware of the role of varied social interactions in her own well-being.

"Those pockets of interactions bring that humanness," says Kadiri. "They bring that connection. They bring a view of how other people's lives are, so you're not just in your own cocoon."

Her days are filled with conversations with people she knows and those she's meeting for the first time – with her family, her housekeeper, her driver, her gardener, the security guard at her workplace, people delivering medical supplies to the clinic where she works, old and new patients and their family members.

She says she especially looks forward to chatting with a woman who sells fruit just outside her housing estate. "I want to get my fruit fresh," she says, "and I've known [her] for eight years that I've been living in this estate."

"All of [these micro-encounters] seem to affirm our belonging, seem to affirm that we are seen and recognized by others, even the most casual contact," says psychiatrist Dr. Robert Waldinger at Massachusetts General Hospital. As the director of the Harvard Study of Adult Development, he has followed individuals and their families for decades to understand the factors contributing to well-being.

Building more social moments into our days doesn't have to be a huge undertaking, he adds. He suggests starting with small steps, like small talk with strangers and acquaintances.

"People love to be noticed," he says. "And most of the time, they will respond positively."

If they don't, he adds, don't give up.

"This is a little like a baseball game where you don't expect to hit the ball every time," he says.

Sometimes, adds Waldinger, these casual conversations can lead to deeper conversations and a greater sense of connection in our lives, which add to our happiness.

In Kadiri's case, her daily conversations with the fruit vendor paved the way for a friendship. Kadiri says she's even helped the woman open a bank account and advised her about health issues. The vendor has said she appreciates the help, but, says Kadiri, "it's a win-win situation" because she feels happier knowing that she's made a difference to someone's life.

A driver who really cares

For some people, those so-called weak ties can be just as important as relationships with friends and family.

In my home country, India, my old friend Anannya Dasgupta lives alone in Chennai. She moved there not long before the pandemic to start a new job as a professor at a university. She has colleagues and close friends in the city but doesn't interact with them every day. And since the pandemic, she has taught many classes virtually.

"So, in a way, for practical support, and even for kindness, and some level of caregiving, [I'm] relying on the so-called weak ties," she says — with the security guards in her apartment complex, her cook and the of drivers she occasionally hires because she doesn't like driving in a city that still feels somewhat unfamiliar to her.

Back in January, when she had a health emergency, she hired a new driver for multiple visits to the hospital. When she had to be admitted for surgery, the man parked her car back at her apartment, gave the keys to the security officer there, then picked up the car to bring her home after discharge.

A few days after she was home, the driver called her just to see how she was recovering.

"My life here," says Dasgupta, "is held up by weak ties."

Readers: Have you had a meaningful encounter with someone you didn't know that you'd like share? Send it to with the subject line "social ties." We may use it in a future story.

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Rhitu Chatterjee is a health correspondent with NPR, with a focus on mental health. In addition to writing about the latest developments in psychology and psychiatry, she reports on the prevalence of different mental illnesses and new developments in treatments.