Pets become family members because they actively shape how we live. “A lot of people who have pets wake up at a certain time, not because of any alarm clock or any need of their own but because their dog needs a walk,” says Irvine. “Just as other humans participate in becoming family by doing these practices—getting up together, eating together, navigating the bathroom times, and all that—so do animals become part of the rituals that make family.”
And it isn’t just a daily ritual that makes pets familial. We form attachments to animals in the same way that we form attachments to people, says Cori Bussolari, a psychologist at the University of San Francisco. She points to a study in Science from 2015 that found when people gazed into a dog’s eyes, both the person and the dog had increased levels of oxytocin. Oxytocin, sometimes called the love hormone, regulates social interactions. It’s released when humans stare into each other’s eyes, and when parents look at their newborn children. “I’m sure if you did the study with other animals it would be the same,” Bussolari says.