It happened by chance. In the late 1960s, psychobiologist Jay S. Rosenblatt and his colleagues at Rutgers University designed a study to look at precisely how caregiving behaviors develop in mother rats. They noticed something remarkable — but not about the mother rats.
The study had a control group made up of rats that had never given birth. After spending just a few days housed with pups, the virgin rats had also started to become maternal. They built nests, carried the pups, even crouched over the babies as if to nurse. Not only that but, the researchers later found, male rats behaved similarly after time with the young, even though they wouldn’t typically be involved in caregiving in the wild.
The researchers’ findings pointed to a big idea, first in rats and later in humans: What we think of as maternal behaviors aren’t only born from the biological processes associated with birth and lactation. They are made possible through the time and attention that parents — whatever their path to the role — give to a baby.
In 2018, I wrote a story for the Globe Magazine focused on the dramatic neurobiological changes that happen when mothers give birth. The story was widely read, and one of the most common questions I heard from readers was, What about me? What about fathers, adoptive parents, and all the other people intimately involved in raising children? Were their stories in the science, too?
They were. Rosenblatt’s early findings in rats have been affirmed and built upon by modern scientists, in other mammalian species, and in humans. Rosenblatt wrote in 1970 that, for rats, maternal behavior is “a basic characteristic” of the species, not dependent on sex for its appearance. Today, researchers are in the process of documenting a “global parental caregiving circuitry” in humans that is thought to be active in all parents really engaged in child-rearing. The mechanisms of change are different for gestational parents and non-gestational parents, but the outcomes seem to be similar. They hinge on the fact that experience matters. A lot.
Babies are powerful stimuli for the brain. Time spent listening and responding to their siren calls, being pulled in by their coos and newborn smell, learning them and letting oneself be learned, too — that’s what ultimately shapes the parental brain.
Brain regions involved in motivation, meaning-making, vigilance and mentalization, or the ability to understand one’s own mental state and others’, show increased activity and connectivity in parents interacting with children. Lots of studies have shown this to be the case in gestational mothers. A small but growing body of research has found a similar pattern in other parents, too.
In one remarkable 2014 study, researchers Eyal Abraham, Ruth Feldman, and colleagues in Israel compared the brains of 41 heterosexual parents, biologically related to their children, and 48 gay fathers, half of whom were biologically related to their child. All parents showed generally consistent engagement of brain regions in the caregiving circuitry as they viewed recordings of themselves interacting with their children, but primary caregiving mothers showed greater amygdala activation than the secondary caregiving fathers (their partners). The gay fathers, who were considered primary caregivers, however, had similar amygdala activation to the mothers. And looking across all fathers, whether or not they were biological fathers, the researchers found, the more time a father spent with his baby, the greater the functional connectivity between the amygdala and the superior temporal sulcus, a cortical region thought to be important in mentalization.
Other studies have documented changes in brain responses in foster parents over time, as they’ve spent more time with an infant, or found similarities in brain activity between adoptive and biological mothers. Many more studies have tracked ways that, in gestational mothers, certain changes in the brain accumulate with experience and seem to last, possibly for a person’s whole life.
“I say as often as I can, good parents are made, not born,” says Darby Saxbe, a psychologist who studies the parental brain and is the founding director of the University of Southern California’s Center for the Changing Family. “It doesn’t have to feel like this thing that you’re either biologically born to do or not.”
Yet, we maintain a deep cultural belief in the supremacy of mothers and the notion that they are naturally equipped with all that they will ever need to be caregivers. This idea actually hurts mothers — underpinning lawmakers’ repeated refusal to pass paid leave for mothers or to embrace it for fathers and other parents. It holds mothers up to be ready-made, fathers to be secondary, and puts families without a gestational mother in a lesser category all their own.
But the science of the parental brain tells us otherwise. The parental brain requires time and exposure to develop. And most adults have the capacity to do it.
Conservative thinkers may frame such statements as demeaning to mothers and the power of maternal love. To me, a mother of two, there is nothing demeaning about acknowledging that power in others who invest in creating it. There is little lost by recognizing that parenting comes from practice and, with it, incredible costs, profound adaptation, and a new way of seeing ourselves and our families.
Chelsea Conaboy is a reporter and editor based in Maine. She is author of the new book Mother Brain: How Neuroscience Is Rewriting the Story of Parenthood. Send comments to firstname.lastname@example.org.