New research has come out that suggests that not only do dog’s have personalities that shift over time, but that their personalities can match that of their owners.

Psychologists at Michigan State University published a paper this month in the Journal of Research in Personality that examined dog personalities. It’s one of the first studies of its kind to look at these possible changes. Researchers surveyed owners of more than 1,600 dogs from a wide range of breeds, from a few weeks to 15 years old. They found that a “dog personality may share similar characteristics to that of human personality.”

“We found correlations in three main areas: age and personality, in human-to-dog personality similarities and in the influence a dog’s personality has on the quality of the relationship with its owner,” William Chopik, a Michigan State professor of psychology and the study’s lead author, said on ScienceDaily.

“When humans go through big changes in life, their personality traits can change. We found that this also happens with dogs—and to a surprisingly large degree,” Chopik said.

“We expected the dogs’ personalities to be fairly stable because they don’t have wild lifestyle changes humans do, but they actually change a lot. We uncovered similarities to their owners, the optimal time for training and even a time in their lives that they can get more aggressive toward other animals.”

As part of the study, owners evaluated their dogs’ personalities in a comprehensive survey and answered questions about their pet’s behavioral history. Owners also filled out a survey about their own personalities. The study found that owners and dogs had a lot in common, personality-wise. They found that extroverts were more likely to own “excitable and active” dogs, whereas people who reported having higher negative emotions were more likely to have dogs described as “more fearful, active, and less responsive to training.”

Moving forward, Chopik plans on investigating how a dog’s home environment influences its personality.

“Say you adopt a dog from a shelter. Some traits are likely tied to biology and resistant to change, but you then put it in a new environment where it’s loved, walked and entertained often. The dog then might become a little more relaxed and sociable,” he says. “Now that we know dogs’ personalities can change, next we want to make strong connection to understand why dogs act – and change – the way they do.”