What Your ZIP Code Says About You

If you’re like most people, you probably don’t know your neighbors very well. Perhaps there are a few familiar faces you say "hi" to as you pass in the apartment hallway. Or maybe there are the neighbors you recognize and wave to as you're driving in or out of your subdivision. And then there’s the old man next door, checking his mail as you’re taking out the trash. You exchange pleasantries but quickly retreat to your own homes.

If you think about the people who live nearby, you can probably find little in common with them. The old retired couple. The young couple with the two little kids and a yappy dog. The other married couple and their sulking teenager with the garage band. The widow and her cats. The yuppie couple that hosts parties every weekend on their deck. The middle-aged man who walks his dog past your house at the same time every day. Their personalities are all so much different from yours—or so it seems.

Social psychologists have long recognized that we think about other people differently depending on whether we perceive them as part of our in-group or our out-group. In particular, we tend to view people in other social groups outside our own as being “all alike.” People tend to think this way when thinking about racial and ethnic groups. But this out-group homogeneity pops up when we talk about the people in rival schools or companies as well.

Likewise, when we think about members of our in-group, individual differences in looks and personality stand out. The Smiths down the street, well, they all look alike, talk alike, and act alike. Even their dog is just like them! But our family, well, each one of us is just so unique and different. And that’s what’s so wonderful about us!

We all belong to many different in-groups. You may not think of your neighbors as an in-group, but they are. They’re the people in your apartment block, compared to those in the apartment block across the street. They’re the folks in your subdivision, versus those in the subdivision on the other side of the road. And if that’s the case, maybe you overestimate just how different you are from other people living nearby.

In a recent article, psychologists Peter Rentfrow and Markus Jokela argue that they can tell a great deal about your personality if they just know your postal code. These researchers are working in a new field called geographical psychology, which studies the ways that psychological phenomena are spatially organized. As it turns out, environments have great effects on individual characteristics. But at the same time, the people actively shape the environments they live in.

Rentfrow and Jokela identify three processes that lead to a clustering of personality types in specific locations. The first process is social influence, which refers to the various ways that people shape each other’s thoughts and behaviors as they interact. Even if you barely talk to your neighbors, they’ve still communicated to you a whole list of expectations, and you know full well what those are. That lawn ornament you inherited from your grandmother? Not in this neighborhood! And maybe you should take better care of the yard. “The grass is looking a bit brown,” mutters the old man next door as he meets you by the mailbox. The neighborhood you live in can affect your attitudes on a variety of moral, political, and social issues.

The second process is ecological influence, which refers to the ways in which natural and man-made features of the environment shape our psychological characteristics. For instance, people with access to green open spaces tend to be happier and experience less stress compared with those who live in concrete jungles. Also, it’s quite true that people on the streets of New York City are less friendly and more aggressive that those you’re meet in Smalltown, USA. It’s not that New Yorkers are inherently nasty people. On the contrary, it could be the crowded, bustling environment of the Big Apple that make people act so pushy and uncaring.

The final process is selective migration, which involves people’s ability (or inability) to move to an environment that suits their personality. When I was a teenager, I had a small group of like-minded friends. We all wanted exciting careers in big cities, and so we all swore we were getting out of the dumpy little burg we were growing up in. And we did.

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Now, when I go back to visit my parents, none of my old friends are there. Like me, they’re all off pursuing careers in big cities. Occasionally, I’ll run into someone I knew from high school, but what have we got in common? My life in foreign countries and major metropolitan areas is simply beyond their ken. And I likewise can’t imagine what it’s like spending one's whole life in the same little town.

We tend to seek out environments that that mesh with our personalities. For example, people who place high value on social relationships prefer to live in small towns where everybody knows everybody else. If that’s the kind of environment they grew up in, they’re likely to stay. But there are also city dwellers who chuck it all for the peace and friendliness of the countryside. Likewise, people who are novelty-seeking or entrepreneurial prefer big cities where there are more opportunities. And they’ll either move or stay put accordingly.

This leaves us with a third group, namely those who are unhappy where they are but can't find a way out. We’ve long known that people who live in deprived neighborhoods suffer from more health problems than those who live in other sections of town. It’s generally assumed that factors like pollution, crime, and lack of access to fresh food are the causes of poor health.

But Rentfrow and Jokela suggest another possible explanation for the correlation between environmental deprivation and poor health. Among the children growing up in deprived, unhealthy neighborhoods, those who are strong enough and smart enough find a way out, leaving behind those who are too ill or otherwise unable to leave.

This discussion reminds me of the old Simon and Garfunkel tune “My Little Town.” That was a favorite when I was hanging out with my high school friends. “Nothing but the dead and dying back in my little town,” we’d sing. Now when I go back to visit, I see that my hometown really isn’t the depressing dump I imagined it to be as a youth so many decades ago. But for those escaping deprivation and destitution, whether from urban slums or toxic coal-mining towns, these lyrics certainly ring true.