Not too long ago, The Economist wrote an article about an academic paper that I’ve since learned is called “Evidence for a conserved quantity in human mobility” by Laura Alessandretti and Andrea Baronchelli, both in the Mathematics Department at City University of London, and Sune Lehmann at the DTU Technical University of Denmark. If you can’t quite get the gist of the paper’s subject from that title, let me tell you what it’s about because it’s pretty fascinating.
It turns out that regardless of where we live – town or country or thriving metropolis -- we generally visit the same places regularly over months and years. Moreover, not only do we tend to visit the same places, but there also is a limit to the number of places we can handle frequenting. On average, the number of places we go to in any given period is limited to 25. Of course, we do discover new places. But if we start going to a new place, an old one drops out. In other words, 25 places is our upper limit – and according to the authors, there’s reasonable evidence that this is not due to lack of time.
So what is it? While the authors don’t yet understand it fully, they are thinking that it is something about us that cognitively limits our geographical behavior. We are not relentless explorers. As The Economist says, we are not the “footloose and fancy-free” creatures we might imagine ourselves to be.
The authors started out by tracking 1000 university students, which showed that students returned to a limited number of places even though the places changed over time. What surprised the authors was that when they expanded the study to tracking 40,000 smartphone users around the world, the general population was similarly geographically limited.
Many questions come to mind here. My first thought was, “Really? Seriously?” My second was, “Do I even make it to 25 places regularly?” My third was, “Only 25?” And my fourth, of course, was “Why?”
There are two things you might think of immediately. One is that we really are creatures of habit. You know it, we all know it. I park in the same parking spot every time I turn up at the pool for my morning swim. I almost always start off in the same direction when I walk my dogs – I don’t even think about it. Habits make it easier to get through the day. They are comfortable. They reduce the cognitive load on us.
But variety also is the spice of life. So we do like finding new places. As Dr. Baronchelli says, “People are constantly balancing their curiosity and laziness. We want to explore new places but also want to exploit old ones that we like.” Yet in any case it’s clear that when new places come in, old places go out.
That brings up the other consideration: that our brains just have limits. The authors of the study suggest that their findings may be very much akin to Robin Dunbar’s work on how many social relationships we can maintain. Dunbar, an anthropologist and psychologist, was the one who found connections between animal brain size and the complexity of their social networks. His conclusion was that the number of people individuals can keep in their social circle maxes out at around 150. That is called the Dunbar number. Actually, there are a series of Dunbar numbers: We are capable of having 150 casual friends, 50 people we’d call close friends (good enough for a dinner party), 15 intimates, and 5 in the closest inner circle. The point is that going over those numbers is too complicated for us to process optimally.
The question all this raises is, given our limits, isn’t it a good thing to force ourselves to jettison the familiar more often than we’d like? Is it possible we could become more creative and more flexible? I read not too long ago in the FT that one man forced himself to order something new off the menu every time he went to same restaurant because he thought it helped him stay flexible in this tech-driven age.
In any case, sticking with the familiar sometimes surely isn’t optimal. Just think of the home-country bias many investors have – that is the preference for Americans to invest in U.S. stocks because it’s familiar and comfortable even when U.S. GDP is only a quarter of world GDP. This is one case where it may well be worth ordering something different off the menu.