Many years ago, I had an old Volvo named Goldy who had an unfortunate tendency to stop dead in her tracks for no discernible reason.

We had just moved to a new city. I needed a desk, and had found one for sale, way out in the sticks. On my way there, traveling along a deserted road, Goldy coughed twice and died.

Repeated attempts to start her were unsuccessful. I was in the middle of nowhere with no cell phone and no traffic to flag down for help. Even if I’d had a phone, I knew no one who could help me. So I started praying. Then a huge motorcycle, complete with large bearded biker, came into view. “This isn’t what I prayed for!” I thought. I wondered if I should get in the car and lock the doors. I had an instinctual fear of this stranger barrelling toward me.

I’ll bet you remember the term “stranger danger.” It was a thing, years ago, to teach kids that all strangers were dangerous. And though it’s long been known that children are most likely to suffer abuse from those closest to them, little kids are still being taught to fear strangers. Since human brains are hardwired to recoil instinctually from that which we judge “different,” it’s no surprise when we react with fear to those whom we don’t know.

But just because a behavior is instinctual doesn’t make it a good idea. 

Social science research is showing that the real danger we face these days stems from the fact that we have ceased to allow strangers into our lives. We isolate ourselves at home, interacting only online. We check our texts rather than exchanging hello’s when waiting in line at the grocery store. We avoid eye contact in public places. We wear headphones even when we’re not listening to music. We go to the post office after hours.

All of this isolation makes us, and our society, sick.

In a recently published summary of studies about human interactions, the social scientists Taylor N. West and Barbara Frederickson have found that those little interactions with people we don’t know—or don’t know well—contribute as much to our wellbeing as our interactions within our closest circle. Friends aren’t enough. People are happiest when they interact with a diverse range of others. Brief encounters with folks we don’t know play a big role in our personal mental health.

And the benefits go far beyond the individual. Connecting with strangers in a positive way builds and maintains the common good. When you take the time to share a smile, or say hello, you are knitting the fabric of resilient community.

Remember that biker I was afraid of so long ago? I didn’t hide in the car; instead, I asked him for help. That man diagnosed the problem with Goldy, contrived a temporary fix and gave me the number of his mechanic. He actually knit me into my new community.

So here’s to knitting our lives together, one stitch—or glance or smile or “hello”—at a time.