When psychologist Darby Saxbe began studying how parenthood shapes the brain, she made a seismic discovery that upended a long-held assumption: that only mothers undergo major biological shifts after a child’s birth. Her pioneering research on what’s now called “dad brain” — the subject of her forthcoming book, Dad Brain: The New Science of Fatherhood and How It Shapes Men’s Lives — revealed that fatherhood changes men’s brains, too.

Saxbe’s work is one example of USC Dornsife’s diverse, cross-disciplinary research on family life. Through the Center for the Changing Family, which she founded in 2020 and continues to direct, scholars from 19 disciplines — including psychology, sociology, economics and neuroscience — explore how families influence everything from mental health to our life chances across generations.

Using tools ranging from brain scans and twin studies to international sociological research and economic analysis, these scholars are working to answer a central question: How do families influence who we are — and how can society better support them? Together, their work reveals just how deeply our closest relationships shape our minds, our decisions — even our physiology.

Birth of “Dad Brain”

When Saxbe joined USC Dornsife in 2013, she set out to study how pregnancy affects mothers’ brains. But conducting brain scans on pregnant women would have been complex and potentially risky. So she flipped the question. “I thought, ‘Why not scan the fathers instead?’” the professor of psychology recalls. Saxbe scanned each father during his partner’s pregnancy, and then again six months after their child was born.

What she found surprised her. Regions of the cerebral cortex — areas associated with attention and executive function — had shrunk during the men’s transition to parenthood. In brain science, a shrinking cortex can signal specialization: The brain is pruning and refining its connections, becoming more efficient at particular tasks. In this case, the change seemed to prepare fathers to tune in more closely to their babies’ needs.

Saxbe also discovered that the more time they spend caring for their infants, the more they lost volume in the cortex. That might sound alarming, but Saxbe is reassuring. She compares the loss of gray matter to editing a draft, streamlining the brain for efficiency and perhaps preparing it to better bond with, and care for, a new child.

Her discovery reframed fatherhood as both a biological and social experience, overturning centuries of thinking and underscoring how family life, in all its forms, is written into our physiology.

But unanswered questions remain. Are fathers’ brainsevolving because dads now spend more time with their children than men of past generations? Or has this biological shift always been there, waiting to be measured?

The answer isn’t clear. At its core, the question reflects a deeper puzzle: How much of family life is hardwired, and how much is learned? Saxbe is sure of one thing — culture and biology are intertwined. “As cultural expectations for fathers shift,” she says, “men’s biology changes, too.”

As cultural expectations for fathers shift, men’s biology changes, too.

Chore Wars

Other USC Dornsife scholars widen the frame even further, looking at how national policies — from family leave to working hours — shape the most intimate, and sometimes the most apparently mundane, details of family life. As sociologist Jennifer Hook has shown, they can even influence who does the dishes.

Hook began exploring the impact of national policies on families more than 20 years ago while working on her PhD, when she set out to answer a stubborn question in American sociology: Why do men do so little housework?

“The conclusion at the time was that we couldn’t really explain it,” says Hook, the Florence Everline Professor of Sociology. Determined to find an answer, she turned to Europe for clues. Analyzing time-use surveys — questionnaires in which people describe how they spend their time — across 25 countries, Hook found a clear pattern that had nothing to do with laziness or chauvinism: Men did more housework when their workweeks were shorter.

“In the United States, we have notoriously long workweeks,” says Hook. “We’ve structured our institutions to make it harder for men to step in. With no paternity leave in the U.S., and little systemic support, fathers simply have fewer opportunities to help out in the home.” In contrast, she found that fathers living in countries with shorter workweeks spent more time with their children, while household chores were more evenly shared.

Double Take: The Twin Equation

While Hook’s research reveals how policy shapes the dynamics of family life, psychologist Laura Baker examines how families themselves influence the individuals within them — and how much of that shaping is influenced by biology.

Few questions are thornier than nature versus nurture in families, and Baker has spent decades trying to solve the mystery.

In 2000, she launched the USC Twin Study, following 750 pairs of 9-year-old twins from Los Angeles. Now in its third decade, it remains one of the largest and longest-running studies of its kind. Unlike adoption research, which examines children raised apart, Baker focuses on twins raised together, creating a powerful laboratory for exploring how traits like aggression, ADHD and even psychopathy emerge.

“We study the personalities of both identical and fraternal twins to see how similar they are to one another,” says Baker, professor of psychology. “If genetic influences are important, then you would expect to see greater similarities between identical twins, who share virtually all their DNA.”

Her findings challenge the widespread assumption that shared environments are the primary drivers of personality. In study after study, identical twins are more alike than fraternal ones — especially when it comes to troubling traits such as low empathy, manipulativeness and psychopathy — suggesting a strong genetic influence.

“For most personality traits,” she says, “family similarities can be explained more by genetics than by shared experience.”

For parents with more than one child, that might come as little surprise. Siblings often have wildly different personalities despite growing up under the same roof. As Baker wryly notes, “Every parent is an environmentalist — someone who believes nurture is more important than nature — until they have their second child.”

Still, she cautions against genetic determinism. A nurturing home environment can protect against harmful traits, just as stress and conflict can amplify genetic predispositions. “You need genes and you need an environment,” she says. “Both are crucial.”

Her work dovetails with Saxbe’s: Biology may set the stage, but family life — our daily interactions, stresses and supports — determines much of the script.

Every parent … believes nurture is more important than nature — until they have their second child.

Breaking the Cycle

That interplay between biology and environment is also central to Gayla Margolin’s research. The Professor Emerita of Psychology has spent decades studying how key elements of family relationships — especially conflict and communication — shape emotional development. Her work also explores how character traits play out in families and how cycles of conflict can be interrupted.

Since the 1980s, Margolin has analyzed families’ daily interactions, beginning with videotaped arguments in the lab and later using smartphones to record real-life moments at home. These snippets helped her track how patterns of conflict and stress escalate or resolve — and how, left unchecked, they can evolve into more serious problems, including violence and child abuse.

As both a clinician and a researcher, Margolin focuses on practical tools, such as communication and conflict resolution skills, that help families shift their dynamics. “As a clinician, I can’t change what people grew up with,” she says. “But I can help them in their day-to-day, moment-to-moment ways of interacting.”

Her research also shows how parents’ relationships set the stage for their children’s future partnerships. “What a child experiences growing up affects what they bring to relationships as an adult,” she says.

The data bears this out. Children who grow up in risky families, with high levels of conflict, emotional and physical abuse, and little support, are more likely to show hostility to their partners later in life. Those patterns can lead to relationship difficulties. Yet, Margolin resists the notion of inevitability.

“Some people believe that it’s destiny,” she says. “But most people break these cycles.”

Her work highlights the tools families use to break free from harmful legacies. Chief among them: better communication. Learning to talk about difficult topics helps reduce tension and prevents destructive patterns. Margolin has seen it happen time and again.

“When we monitor people’s physiology while they talk about the hard things,” she says, “we can actually see their physiological arousal decline. This decline in arousal between romantic partners can be contagious, especially when partners experience each other as a ‘safe haven’ as they reveal heartfelt information. That’s where change begins.”

It Takes a Zip Code

While Margolin examines family life within the home, economist Ashlesha Datar explores how families interact with the world around them. Her research shows that the neighborhoods children grow up in play a powerful role in determining their health.

As director of the Program for Children and Families at the USC Dornsife Center for Economic and Social Research, Datar studies how both family life and the broader environment influence children’s risk of obesity. Research has long shown that kids who live near parks or green spaces tend to be healthier. But Datar questioned whether that was cause or coincidence.

“It’s all very correlational,” she says. Families who live near a park may already prioritize health or simply have the means to choose such a neighborhood. “It’s not as if the park was randomly dropped next to them.”

What she wanted was a way to study what happens when families are, in effect, randomly assigned to different neighborhoods — an experiment too impractical to design. But then she remembered her own childhood in a military family. Frequent moves, dictated by postings rather than preferences, created what’s known as “a natural experiment.”

Analyzing health data from military families, Datar noticed a striking pattern: Moving from a low-obesity area to a high-obesity one increased a family’s risk of weight gain — and vice versa.

Her findings make a clear case that neighborhoods influence health. But Datar stresses that, just as genetics or family history aren’t destiny, the environment isn’t, either. Family matters, too. Teenagers with stronger self-control — a trait influenced by both genes and upbringing — gained less weight than their peers, even in high-risk neighborhoods. Personality acted like armor against the environment.

“And that,” she says, “is where family comes back into play — shaping the people we become, and the futures we’re able to create.”