Dog owners will tell you that their canine companions have personalities, and a new study from Michigan State University says those personalities are likely to change over time.

The study, published in the Journal of Research in Personality, found that dogs’ personality change, much like humans.

“When humans go through big changes in life, their personality traits can change,” the lead author, professor William Chopik, said in a university release. “We found that this also happens with dogs ― and to a surprisingly large degree.”

“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,” he added. “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.”