The Hot Dog Stand Wave That Sparked a Happiness Study

A Wave Exchanged at a Hot Dog Stand

During her graduate school years, psychologist Gillian Sandstrom worried about whether she could handle the academic workload. Between her lab and her advisor’s office stood a hot dog stand, and every time she passed the woman working there, they’d smile and wave at each other. They never actually spoke, but Sandstrom says just having someone who recognized her and greeted her made her feel like she belonged at the school.

In an essay describing her own experience, Sandstrom explains that this simple greeting became the seed of her research. She found herself wondering: beyond deep conversations with close friends, could the brief hellos we exchange in daily life also shape our mood and sense of belonging?

Does Talking to People You’re Not Close to Actually Help

“Weak ties” describes relationships where you know someone but aren’t especially close. Think of the barista at your neighborhood café or a neighbor you exchange greetings with occasionally. Coworkers can fall into either category, depending on how close you actually are. Sociologist Mark Granovetter explained in 1973 how these relationships play a role in accessing new information and job opportunities. Sandstrom studied the same kind of relationship through the lens of happiness and belonging.

In a 2014 study, Sandstrom and Elizabeth Dunn had participants log who they interacted with each day and how much. They distinguished between interactions with close ties and interactions with casual acquaintances, then examined how each type related to that day’s mood and sense of belonging.

On days when participants interacted with weak ties more than usual, they also reported higher happiness and stronger belonging. This relationship held even after accounting for how much they’d interacted with close ties that day. That said, since this was an observational study of daily life, it couldn’t fully separate whether conversation improved mood or whether a good mood simply led to more conversation.

The same research team’s 2014 barista experiment asked participants to behave differently at a coffee shop. One group was told to complete their order quickly and efficiently; the other was told to make eye contact, smile, and have a brief chat with the employee. The group that talked reported feeling happier and more connected after placing their order. The finding suggests that even light, surface-level contact—without any deep conversation—can boost mood.

Sandstrom also cites other studies on conversations with strangers. Participants tended to expect the conversation would be awkward, but afterward reported it had actually been more enjoyable than they’d anticipated. Of course, not every conversation turns out pleasant, and the other person may not want to talk at all. That’s why the advice to start with something low-stakes—a simple greeting—is practical.

The Link Between Relationship Diversity and Happiness

Hanne Collins’s research team analyzed data from over 50,000 people across 8 countries in a study published in PNAS¹ in 2022. They looked at how evenly people interacted across different types of relationships—family, friends, colleagues, acquaintances—calling this “relational diversity.” People who interacted across a wider variety of relationships showed higher levels of happiness and life satisfaction.

The analysis drew on four datasets: 578 participants from a US survey, 19,197 respondents from the American Time Use Survey, 10,447 participants from the WHO Study on Global Ageing, and 21,644 users of a French mobile app. What stands out is that a similar association appeared across all four independent datasets.

Relational diversity isn’t simply about how many people you talk to. Meeting the same ten people looks different depending on whether they’re all coworkers, or a mix of family, friends, and neighbors. What the researchers examined was how a person’s daily interactions were distributed across these different types of relationships.

The link between relational diversity and happiness held up even after accounting for total interaction time or frequency. That doesn’t mean the amount of conversation or the value of close friendships doesn’t matter. It’s better read as evidence for reflecting on whether you’re maintaining close relationships well while also having opportunities to connect with others beyond them.

Besides the US and France, the data also included sources from Ghana, India, and China. The researchers note, however, that they cannot rule out the possibility that happier people simply happened to meet a wider variety of people. While it’s plausible that having many kinds of relationships can broaden one’s sense of belonging, there’s no basis for claiming this effect is guaranteed for everyone.

In Korea, Where More People Live Alone

It’s worth examining how many chances people living alone in Korea actually have for conversation and mutual support in daily life.

According to the National Data Agency’s “2025 Single-Person Households in Statistics,” Korea’s single-person households numbered 8.045 million in 2024, accounting for 36.1% of all households. Among single-person households, those aged 70 and over made up 19.8%, while those 29 and under made up 17.8%. This is a composition that makes it hard to think of people living alone as simply young office workers.

In the 2025 Social Survey cited by the same report, 48.9% of single-person household respondents said they often or sometimes feel lonely. Among all respondents, the figure was 38.2%—a gap of 10.7 percentage points between the two groups. Not everyone living alone feels lonely, but more respondents in single-person households reported feeling lonely.

Whether there’s someone to turn to for help is also worth considering. Among single-person household respondents, 68.9% said they had someone to help them when physically ill, and 73.5% said they had someone to talk to when feeling depressed. Both figures were lower than among all respondents. Beyond a casual greeting, I find myself thinking that people also need relationships they can reach out to in difficult times.

The WHO launched its Commission on Social Connection in 2023, and its 2025 report treated loneliness and social isolation as public health issues. Loneliness is tied not only to mental health but also to physical health. Still, we shouldn’t take these health studies and directly link them to the effect of a brief greeting, as if a single hello could prevent illness or a lonely death.

Changes in daily life are also worth thinking about. When ordering and paying are handled entirely through an app, there’s less need to exchange words with staff. This isn’t to say convenience itself is the problem. Rather, as life gets more convenient, it’s worth checking how many opportunities remain for meeting and talking with other people.

Working From Home and Everyday Conversation

Working from home cuts your commute, but it can also shrink the chance encounters you’d otherwise have at the office. If you spend most of your time working from home, it’s worth examining what kind of interaction you’re getting beyond work-related messages.

There’s the person you pass in the elevator on your way in, the security guard in the lobby, the small talk with staff at the restaurant where you grab lunch. Video calls can carry the workload, but they don’t reproduce these incidental encounters on their own. In a remote-work setup, you may need to deliberately carve out time for small talk and checking in with others.

A 2022 study of 1,511 Norwegian workers found that working from home was positively associated with loneliness and negatively associated with workplace bullying. Since this was based on a single-point-in-time survey, it can’t confirm that remote work caused either change. Still, it shows that when evaluating where you work, you need to weigh engagement, relationship quality, and loneliness together.

A study analyzing 13,468 Japanese office workers compared 4,052 remote workers against 9,416 non-remote workers. The group working from home four or more days a week reported loneliness somewhat more often, but once other factors were controlled for, the difference didn’t reach statistical significance. What emerged more clearly from this study was that a lack of support from supervisors and colleagues was associated with a higher likelihood of feeling lonely.

Relationship quality also looms large in long-term research. Robert Waldinger, who leads the Harvard Study of Adult Development², explains that participants who reported greater satisfaction with their relationships at age 50 were healthier at age 80. That finding covers close relationships too — family, spouses, and the like. It invites us to weigh the value of light, casual interactions alongside the support we get from the people closest to us.

Oswarld’s Lens

Honestly, this topic hits close to home for me.

Once I started my own company and began working as an independent consultant, the number of people I talked to in a day dropped sharply. There were things I never noticed when I worked at a company. Passing a colleague from another team in the hallway with a casual “take care,” exchanging a glance with the person next to you in the cafeteria, showing up five minutes early to a meeting room and making small talk. All of that was weak ties.

Now I work at my monitor all day, and on some days the only face-to-face exchange I have is a “thank you” to the convenience store clerk in the evening. Looking at it through Collins’s concept of “relational diversity,” the range of relationship types I talk to in a day has shrunk down to almost one.

When I build a go-to-market strategy, I look not just at the launch event but at the everyday moments when customers keep encountering the product. Reading this piece made me reflect on my own life in similar terms. Before scheduling some big gathering, I think I need to first look at who I’m talking to, and what I’m saying, every single day.

A plan to make a great new friend seems harder to execute right now than simply adding one more greeting to the people I already run into every day. That’s exactly why research on brief conversations feels useful to me.

That said, some people may find it uncomfortable to suddenly strike up conversation with a stranger. I think a realistic starting point for me, too, is just greeting the people I already encounter daily. Instead of a passing nod to the security guard at my apartment building, I could make eye contact and say, “take care.” And if the other person is busy or doesn’t feel like talking, a short greeting is enough to leave it at that.

Closing

What I’ve taken away from this research is that even small, everyday exchanges are worth paying attention to. Alongside nurturing relationships with close friends, I’m also trying to notice how I greet neighbors or staff I run into often.

There’s no need to force yourself to expand your circle of relationships. What kind of change is needed will depend on whether you feel comfortable spending time alone, whether you have someone to reach out to when you’re lonely, and whether you exchanged a simple greeting with anyone during the day.

Tomorrow morning, you might try greeting someone you pass by every day a little more clearly than usual. You don’t need to have some grand topic ready. Sometimes it’s simply reassuring to feel that there’s someone out there who recognizes you and says hello.

References & Further Reading

Primary sources

• Sandstrom, G. M. & Dunn, E. W., “Social Interactions and Well-Being: The Surprising Power of Weak Ties”, Personality and Social Psychology Bulletin, 2014. : This study looks at how weak ties shape everyday happiness and a sense of belonging.
• Collins, H. K. et al., “Relational Diversity in Social Portfolios Predicts Well-Being”, PNAS, 2022. : This paper analyzes the link between the diversity of one’s relationships and overall happiness.
• Sandstrom, G. M. & Dunn, E. W., “Is Efficiency Overrated? Minimal Social Interactions Lead to Belonging and Positive Affect”, Social Psychological and Personality Science, 2014. : The original paper behind the Starbucks barista experiment.

Background

• Waldinger, R. & Schulz, M., The Good Life: Lessons from the World’s Longest Scientific Study of Happiness, Simon & Schuster, 2023. : Drawing on the Harvard Study of Adult Development, this book tells the story of how relationships shape health and happiness. It was published in Korean by Businessbooks under the title The World’s Longest Report on the Pursuit of Happiness.
• National Data Office (Korea’s national statistics agency), “2025 Single-Person Households in Statistics”, 2025. : Household figures are from 2024; social-relationship indicators such as loneliness are from 2025.
• WHO, Social Isolation and Loneliness and the 2025 report of the Commission on Social Connection: These cover the relationship between loneliness and health.

The author is Oswarld (Kwangseob Ahn). Current roles: Adjunct Professor at Sejong University, Strategy Consultant at INLEVEL9. Career, research, books, and recent work are kept current on the About page. Latest · July 2026: HEMA-2: A Consolidation-Aware Tri-Memory Architecture with Multi-Channel Scheduling for Lifelong Conversational AI.

Footnotes

1. PNAS (Proceedings of the National Academy of Sciences) is a journal published by the U.S. National Academy of Sciences, covering research across the natural and social sciences. ↩

2. The Harvard Study of Adult Development is a long-running study that began in 1938. It has tracked the lives and health of distinct groups — including Harvard students and teenagers from Boston — and later expanded to include their spouses and children. ↩