You’re walking to the shops, or waiting at a pedestrian crossing, and someone you’ve never met catches your eye and smiles. For a split second you have to decide what to do. Smile back? Say hello? Look away and pretend you didn’t notice?
It seems like a small moment, and it is. But psychologists have looked closely at moments like this, and their findings suggest that how we respond matters more than we might think, both to the stranger and to ourselves.
Your face may already be answering
Part of the response happens before we decide anything. In a study published in Psychological Science in 2000, Ulf Dimberg, Monika Thunberg and Kurt Elmehed showed people pictures of happy and angry faces for just 30 milliseconds, hidden behind neutral faces so quickly that participants weren’t aware of seeing them. Sensors on their faces still picked up small muscle reactions that matched the expressions they had been shown.
In other words, a flicker of a returned smile can begin without any conscious choice.
Being seen matters, even by a stranger
The most direct evidence that these tiny exchanges count comes from a simple experiment on a university campus. Eric Wesselmann, Kipling Williams and colleagues had a research assistant walk along a busy path at Purdue University in the United States and do one of three things as they passed a stranger: make eye contact, make eye contact and smile, or look straight past the person’s eyes, as though they weren’t there.
A second researcher then stopped the passer-by and asked how disconnected they had felt from others in the past minute. Those who had been looked through reported feeling more disconnected than those who had received eye contact, with or without a smile. The study was published in Psychological Science in 2012.
The effect was brief, and it was measured only a moment later. But it shows something worth keeping in mind. When a stranger smiles and we look away, they may feel it, even if only for a minute.
Small exchanges can lift your own mood
Responding warmly isn’t only a kindness to the other person. In a 2014 study, Gillian Sandstrom and Elizabeth Dunn asked customers at a coffee shop either to be as efficient as possible when buying their coffee or to smile, make eye contact and have a brief conversation with the barista. Those who made the small social effort came away in a better mood, and the researchers found early evidence that a greater sense of belonging explained the difference.
Other research points the same way. In experiments on Chicago trains and buses, Nicholas Epley and Juliana Schroeder found that commuters asked to talk to a stranger had a more positive journey than those who kept to themselves, even though most had predicted the opposite.
For people whose daily contact has shrunk, perhaps after leaving work or moving to a new area, these brief moments may be a bigger share of the day’s social life than they used to be. A returned smile is one of the easiest to say yes to.
A smile doesn’t mean the same thing everywhere
If you travel, it helps to know that smiling at strangers isn’t read the same way in every culture. In a study of 5,216 people across 44 cultures, published in the Journal of Nonverbal Behavior in 2016, Krys and an international team of colleagues found that attitudes to smiling individuals varied widely. In some cultures, people who smiled were judged as less intelligent. In societies with high levels of corruption, a smile tended to reduce rather than increase trust.
So a stranger who doesn’t smile back on holiday isn’t necessarily being unfriendly. And a stranger smiling at you at home may come from a place where smiles are given more freely, or more sparingly, than you’re used to.
How to respond
Put together, the research suggests a few simple options. None of them needs to be more than a second or two.
- Smile back. It’s the natural response, and your face may already be halfway there.
- Make brief eye contact. Even without a smile, being acknowledged is what made the difference in the Purdue experiment.
- Add a nod or a word. “Morning,” or “Lovely day,” is enough. If the moment invites more, such as in a queue or on a bench, a short chat can be a pleasant surprise for both of you.
- Don’t overthink it. A slightly late or lopsided smile is still a smile.
When you’d rather not
None of this means you owe a stranger a response. If a smile feels unwelcome, or something about the situation makes you uneasy, it’s fine to look away and carry on. Trusting your instincts about safety comes first, and nothing in this research suggests otherwise.
Most of the time, though, a stranger’s smile is just what it seems: a small gesture of goodwill. Returning it costs nothing, and the evidence suggests both people walk away feeling a little more connected.
Representative image. Photo: SHVETS production / Pexels
