Emotional Power Broker of the Modern Family

“The big bone of contention was that my mom and my sister thought that he was too smart to be treated like a dog; they thought he was a person and should be treated as such — well, spoiled,” said Danielle, a Florida woman who asked that her last name not be published to avoid more family pet strife. “The dog remains to this day, 10 years later, a source of contention and anger.”

Psychologists long ago confirmed what most pet owners feel in their bones: that for some people bonds with animals are every bit as strong as those with other humans. And less complicated, for sure; a dog’s devotion is without detectable irony, a lap cat’s purring without artifice (if not disapproval).

Yet the nature of individual human-pet relationships varies widely, and only now are scientists beginning to characterize those differences, and their impact on the family. Pets alter not only a family’s routines, after all, but also its hierarchy, its social rhythm, its web of relationships. Several new lines of research help explain why this overall effect can be so comforting in some families, and a source of tension in others. The answers have very little to do with the pet.

“The word ‘pet’ does not really capture what these animals mean in a family, first of all,” said Froma Walsh, a psychologist at the University of Chicago and co-director of the Chicago Center for Family Health. The prevalent term among researchers is now “companion animal,” she said, which is closer to the childlike role they so often play.

“And in the way that children get caught up in the family system as peacekeepers, as go-betweens, as sources of disagreement, the same happens with pets.”

People cast these roles in part based on the sensations and memories associated with their first Princess or Scooter, psychologists say — echoing Freud’s idea of transference, in which early relationships provide a template for later ones. In many families, this means that Scruffy is the universal peacemaker, the fulcrum of shared affection.

In a family interview reviewed by Dr. Walsh in a recent paper, one mother said that the best way to end an argument between siblings was to bark, “Stop fighting, you’re upsetting Barkley!” “This is always more effective than saying, ‘Stop hitting your brother,’ ” the mother said. (Barkley made no comment.)

Animals often sense these expectations and act on them. In a video recording of another family discussed in the paper, the cat jumps on a woman’s lap when it senses an impending argument with her husband. “And it works,” Dr. Walsh said. “It reduces tension in both; you can see it happening.”

“She’s my first child,” said Adrienne Woods, a cellist in Los Angeles, of Bella, the Husky puppy that she and her fiancé just got. “The biggest upside is this sense of inner peace. I feel like a grandma, like I have a companion I’ve been wanting for 30 years.”

Yet pets can also raise tension, as millions of couples learn the hard way. The Animal Planet show “It’s Me or the Dog” is built on such cases. And Cesar Millan, a dog behavior specialist, has become a celebrity by helping people gain control over unruly hounds, bringing order into households with uncertain lines of authority.

Perhaps more often, pets become a psychological wedge not from lack of boundaries but because family members have diverging views of what a pet should be. And those views are shaped by cultural inheritance, more so than people may realize.

In a study of dog ownership, Elizabeth Terrien, a sociologist at the University of Chicago, conducted 90 in-depth interviews with families in Los Angeles, including Ms. Woods. One clear trend that has emerged is that people from rural backgrounds tend to see their dogs as guardians to be kept outside, whereas middle-class couples typically treat their hounds as children, often having them sleep in the master bedroom, or a special bed.

When asked to describe their pets without using the word “dog,” people in more affluent neighborhoods “came up with things like child, companion, little friend, teenage son, brother, or partner in crime,” Dr. Terrien said. In neighborhoods with a larger Latino immigrant population, owners were more likely to say “protector,” or even “toy for the children,” she found. “In those neighborhoods you’ll sometimes see kids yanking around a dog on the leash, pushing and playing, the sort of behavior that some middle-class owners would think of as abuse,” she said.