When the Jewish German psychologist Kurt Lewin fled Nazi rule and moved to the United States in 1933, he, like many immigrants, found his new home a little puzzling. Especially when it came to friendships.

“Compared with Germans, Americans seem to make quicker progress toward friendly relations early in the acquaintance process and with many more persons,” he wrote in his 1936 paper “Some Social-Psychological Differences Between the United States and Germany.” “Yet this development often stops at a certain point and the quickly acquired friends will, after years of relatively close relations, say good bye as easily as after a few weeks of acquaintance.”

Lewin thought that this idea of friends as fast fashion—easily acquired, emotionlessly discarded when worn out—might be spurred by the United States’s high level of residential mobility. American society was mobile in his day and has only gotten more mobile since. People can move from sea to shining sea, dropping things as they go.

Research by Shigehiro Oishi at the University of Virginia has shown that moving residences is sometimes associated with shallower or lower quality social relationships—especially for introverts, who may find it harder to replace the friends they’ve left behind.

And a new paper by Omri Gillath at the University of Kansas and Lucas Keefer at the University of Dayton suggests that the more someone moves from place to place, the more likely they are to think of their relationships as disposable—because they’re used to thinking of things as disposable.

Gillath and Keefer did a series of small studies where people took questionnaires about their willingness to dispose of things and people and their history of moving from place to place. They found that people who’d moved around a lot were more willing to get rid of objects (presumably because they have to do a culling of their possessions when they move), and being willing to get rid of things was associated with being willing to cut social ties. And in an experimental study where they primed people to think about moving in the future before they took the “willingness to dispose” survey, even if they didn’t have a nomadic history, they saw the same results.

Moving is a big life change, and not only with regard to place. Unless someone just moves across town, or to the next town over, the social circles they have easy access to are also likely to change, which, the researchers suspect, is the largest factor in why people might let some friends go. (Throughout the studies, they found no difference between romantic relationships and friendships as far as disposability, which is interesting and maybe reflective of friends being equally valued as significant others.)

This isn’t to suggest that people view their friends as objects, or “disposable” in the same way as a weird tangle of old cords at the back of the closet. But “moving also requires making choices about which relationships are ‘worth’ maintaining and which are not, which ties could be replaced and which ties should be maintained,” Gillath and Keefer write. We can maintain them—we have the technology—but effort put toward long-distance phone calls and Facebooking is effort not put toward making new friends in the new place. It’s a complex calculation. And chances are, people will have many opportunities to make these assessments—one study that followed best-friend pairs for 19 years found that people moved an average of 5.8 times over that time.

The researchers acknowledge that the associations they found are only part of a complicated picture. For some, being extra mobile might make them lonely and might motivate them to put extra effort into their long-distance relationships. But they might put more effort into staying in touch with their best friends while they let some less-close friendships fall into remission.

Perhaps this occasional tendency to keep friendships from getting too deep, and being willing to let them go, that Lewin characterizes as particularly American, comes not only from an easy-come, easy-go flippancy borne of mobility, but the knowledge of how hard it is to leave people. As John Reisman puts it in his 1979 book Anatomy of Friendship, as part of a discussion of Lewin’s claims: “Within a disruptive, changing, discontinuous society, people could, by keeping their friendships at an associative level, protect themselves from the sadness and self-blame that can be brought about when they have to sever close relationships.”