Every year, nearly three-quarters of a million people around the world become new parents. Many might remember feeling overwhelmed during those first weeks and months with their new baby. But research by Marc H. Bornstein, PhD, suggests that new parents may be more prepared for their role than they realize: He's found that humans' neural circuitry primes us to respond and interact with babies in ways that are key to our infants' development.

Bornstein, the head of the Child and Family Research Department at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (and a father of two himself), has long believed that parenting merits its own field of study. In the late 1990s, he founded the journal Parenting: Science and Practice and published the landmark five-volume "Handbook of Parenting."

In recent years, he's become interested in the behavioral neuroscience of parenting — how our brains are wired for rearing children, and how parenting might actually shape our brains. Such research, he says, may help us understand how people can become better parents, and why parenting sometimes goes awry, as in cases of abuse and neglect.

Bornstein spoke to the Monitor about his and others' work in the new field.

Why should parenting be considered its own field of scientific study?

If you look at the history of psychology, people have always studied parenting, but they've approached it either through traditional social psychology or from a child development angle. But at the intersection of those two approaches was a domain of study in and of itself: parenting. Given that every person who has ever been born and lived on earth has had parents, and that most people become parents, it seemed to me that parenting as a scientific domain merits attention on its own.

You have found evidence that all people — whether parents or not — are in some ways built to respond to babies. Can you discuss that?

This is a really new — and when I say new, I mean the last five years — developing literature, and so we're still figuring out which regions of the brain are the ones to look at.

In one recent study, we used fMRI to examine the brains of people as they looked at photos of infants versus adult humans, dogs, cats, kittens and puppies. We saw increased activity in response to the infant faces in the inferior frontal gyrus, an area associated with emotion, empathy and face recognition. So, adult faces and animal faces excited that area, but infant faces excited it even more — the baby face is somehow special.

But the most interesting thing that we saw in the study was increased excitation in the supplementary motor area. It's a part of the brain that's involved with planning and organization relative to movement. It's also the starting mechanism for speech. So, seeing a baby's face appears to get you ready to talk to the baby, gets you ready to move and do something, perhaps with respect to the baby.

This makes sense because when you do behavioral observations, people naturally talk to babies even though they know that babies don't understand language. Not only that, but people also talk to babies in a special speech register called infant-directed speech. People often don't even realize they're doing it, and it's practically universal. People all around the world respond to babies this way.

Are there gender differences in how people's brains respond to babies?

There's evidence that men's and women's brains respond to infant cues differently. We recently used fMRI to investigate how men and women respond to infants' hunger cries. We found that when women — both parents and non-parents — heard the cries, activity decreased in their dorsal medial prefrontal and posterior cingulate areas. Those are the areas that are active when your mind is at rest, suggesting that the women in the study "snapped to attention" when they heard the cries. For men, though, activity stayed the same in those areas.

You and others have also found evidence that the brain changes in some ways, in response to parenting's demands. Can you discuss that?

It used to be thought that the brain was more or less a fixed structure. We now know that it's extremely plastic … and that different regions of the brain can be influenced by experience. One study that got a lot of play was on London taxi drivers. The researchers found that the region of the hippocampus that is used in mapping spatial relations was enlarged in London taxi drivers relative to controls, and it was more enlarged in those who'd been driving taxis longer than those who hadn't. Other studies of stringed-instrument players, Braille readers, jugglers and even students studying for exams show this same neuroplasticity.

So, it occurred to me that having a baby is a nontrivial kind of experience that changes the kinds of stimuli that you're exposed to, and that also drives this neuroplasticity.

For example, some research has found that mothers' brains actually grow in size in the early months of parenting. In the first three months after their babies were born, gray matter in mothers' brains increased in certain areas, including the hypothalamus, amygdala and prefrontal cortex, related to motivation, reward and emotion processing, and reasoning and judgment.

There are also a variety of studies now that use MRI to look at parents' responses to children's faces, or stimuli like crying sounds. Some of them show that certain regions of the brain, such as the insula or the thalamus — which have been associated with emotion and reward — are excited by infant stimuli, and sometimes by your own infant more than a stranger's infant.

And if you also ask the parents about their investment in parenting or their degree of warmth toward their own child, there are correlations between how people rate themselves as a parent and some of these brain responses. So, their brain activity is related in a systematic way to their parenting cognitions or behaviors.

You run a cross-cultural parenting study at the National Institutes of Health, in addition to the behavioral neuroscience research. Can you talk about that study?

The two studies are independent, but they complement one another. I have a longitudinal study going on, where we see the families at five months, 13 months and 20 months. And I recruited a network of colleagues in 14 countries around the world to do parallel studies. So, for example, at five months we go into the home and videotape an hour of mother-infant interaction and then we code the videotapes using a system I developed.

I have 20 modes in which I code everything that the baby does and everything that the mother does and the entire environment around them. I can look, for example, at how often and when mother vocalizes to baby. And I can look at if the baby starts to fret and what the mother does [in response] in different cultures.

In our analysis, we've found that by the time a baby is 5 months, mothers will reliably vocalize to a baby within two seconds of the baby ending vocalizing to the mother. What's interesting about that cross-cultural result is that if something is true behaviorally across cultures, you might expect that it would be a candidate for something that would be deeply embedded in the brain. And lo and behold, as I mentioned earlier, we've also found that if you show a picture of a baby to an adult, the starting mechanism for speech is what gets excited.

So the cross-cultural behavioral studies give you clues about which "universals" of parenting are likely embedded in the brain?

Right, which is why I call this new field "a behavioral neuroscience of parenting." I'm not interested in going into the brain just to see what lights up. I'm interested in knowing how the brain developed and functions for real-world adaptations. Parenting, in my view, is a multilevel phenomenon. And we study it from a biological perspective, from a behavioral perspective and from a cultural perspective, in order to understand how it works and how it functions.

What's next for you and your lab?

The fMRI approaches that I mentioned allow you to peer into the brain and see which regions and networks are activated — this is a spatial view. One approach we are pursuing in the near term asks instead about the temporal domain, and stages of information processing in parents' and infants' brains.

In one study, mothers brought 3- and 6-month infants to the lab. We took pictures of both the infants and the mothers and then hooked each up to an EEG net that allows us to monitor activity at the scalp. We analyzed mothers' responses to the faces of their infants versus similar looking infants, and infants' responses to their mothers versus similar-looking adult females. We found that, by the time a baby is 3 months of age, mothers' brains have become attuned to the faces of their infants, and infants' brains to their mothers' faces.

In the longer term, we are interested in studying whether and how the brains of teen moms, as well as atypical — depressed, abusing and neglecting — parents, and dads, may be similar to or different from one another and how they relate to actual parenting practices.