Most people spend part of every day surrounded by strangers, whether on their daily commute, sitting in a park or cafe, or visiting the supermarket.
Yet many of us remain in self-imposed isolation, believing that reaching out to a stranger would make you both feel uncomfortable.
These beliefs may be unwarranted. In fact, our research suggests we may often underestimate the positive impact of connecting with others for both our own and others' wellbeing.
For example, having a conversation with a stranger on your way to work may leave you both feeling happier than you would think.
We asked bus and train commuters in Chicago how they would feel about striking up a conversation on their morning commute, compared to sitting in solitude or doing whatever they normally do. Most thought that talking would lead to the least pleasant commute.
However, when we actually carried out the experiment, those randomly assigned to talk had the most pleasant commute.
Our commuters estimated that only about 40% of their fellow train passengers would be willing to talk to them. Yet every participant in our experiment who actually tried to talk to a stranger found the person sitting next to them was happy to chat.
Thinking others aren't interested in talking, or won't like you, are the very things that will keep you from making contact.
In fact, research suggests that we consistently underestimate how much a new person likes us following an initial conversation.
The inner lives of strangers
Separate experiments on buses and in taxis yielded similar results; individuals found connecting with strangers was surprisingly pleasant.
The positive impact even seems to spread to the person you talk to. In another experiment conducted in a waiting room, we found that not only did the people we encouraged to talk have a more pleasant experience, but so did the person they were asked to talk to.
Of course, nobody appreciates unwanted attention.
But simply reaching out to a fellow human being to say hello may be better received than people realise. Few start a conversation with a stranger, but most seem happy to talk if you reach out with good intentions.
One reason may be that the experience of talking with others and hearing a stranger's voice makes us realise they have a rich inner life of thoughts, feelings, emotions, and experiences, just like us.
These brief connections with strangers are not likely to turn a life of misery into one of bliss. However, they can change unpleasant moments - like the grind of a daily commute - into something more pleasant.
Humans are inherently social animals, who are made happier and healthier when connected to others. Feeling isolated and lonely, in contrast, is a stress factor that poses a health risk comparable to smoking and obesity.
Professor Epley's team has replicated the Chicago experiment with nearly 700 rail commuters on Greater Anglia's lines into London for the BBC.
He will offer early impressions of the results on Friday as part of Crossing Divides On the Move, a day when the BBC - working with transport companies - is encouraging adults to chat to fellow passengers.
- Virgin Trains designating all coach Cs on its west coast services as the "chat coach"
- Arriva distributing "conversation starter" cards via its national bus network, and encouraging passengers to "share a smile"
- Encouraging people from different backgrounds to mix on Translink Northern Ireland's Glider service connecting East and West Belfast
You might imagine that only outgoing people would benefit more from connecting with others.
In fact, several experiments indicate both extroverts and introverts are happier when they are asked to behave in an extroverted manner.
We found that commuters tend to be happier when they talk to a stranger, regardless of how extroverted they perceived themselves to be.
Although personality may not have a big effect on your experience of connecting with others, it may affect your expectations, with introverts underestimating the positive consequences of interaction.
Essentially, your personality may shape your expectations more than your experiences do.
Our expectations can become self-fulfilling. If you think that talking to a stranger is likely to be unpleasant, you'll never try and so never discover that your expectations might be wrong. This can keep us mistakenly isolated and disconnected from others.
This may help to explain why cities seem so crowded with highly social people who are actively trying to ignore each other. Strangers sit next to each other on park benches staring at their phones, walk down city streets without smiling or saying "hello" to anyone.
Random acts of kindness
These misunderstandings extend beyond interaction on public transport to many areas of our lives, where we consistently underestimate the positive impact of reaching out to others in general.
Those who write a thank-you letter, do random acts of kindness, or express compliments consistently, believe their recipient will be less happy than they actually are.
Underestimating the positive impact of reaching out can keep us from being social enough for both our own, and others', wellbeing.
Our findings do not suggest that you should talk to every person you see, or that you should engage with everyone who attempts to approach you.
Instead, the next time you'd like to help a stranger with something, or strike up a conversation, but are worried about how they might react, simply give it a try.
Our research suggests it's likely to go significantly better than you might expect, leaving both of you feeling happier and better connected.
About this piece
This analysis piece was commissioned by the BBC from experts working for an outside organisation.