A lot of weird stuff starts to happen when you get comfortable with someone: Depending on your attachment style, you might consider joining finances or even give each other the pet test to determine your compatibility when it comes to having kids. No matter how you express your comfort level with your S.O., a new study by researchers at the University of London uncovered that a constant in most long-term relationships is automatic motor imitation — or, more simply, a couple’s tendency to imitate each other’s movements.

Man and woman lie on the lawn

“In relationships that are very close, we act as if characteristics of the other individual are partially our own, reflecting an overlap between cognitive representations of self and close others,” the study says.

By studying the body response of 21 participants, the study gleaned that, as relationships grow, the line between self and other begins to blur. While the results were constant despite gender and ethnicity, the researchers found that a specific attribute, in particular, affected the response of the participants: attachment style.

According to the study, people with anxious attachment styles had a higher tendency to imitate their partner. An anxious attachment style is “characterized by fears of abandonment, which drive a desire for increased personal closeness,” the study said. Basically, people who need closeness in a relationship imitate their partner because it makes them feel closer to them.

While it’s interesting that we imitate those we love, the study also hints at something deeper: As we grow closer to someone, we subconsciously sacrifice part of our sense of self in order to develop intimacy with that person. Talk about chemistry!

Have you and your boo been together so long that you’re totally twinning? Tell us how @BritandCo!

(Photos via Getty)