What Happens to A Man’s Brain When He Becomes A Father?
You’re not born a parent — you become one. And while having children undoubtedly comes with its costs, could it also bring unexpected benefits?
Increasingly, science is revealing that the brains of both women and men undergo real changes when they become parents. Though research on fathers still lags behind, the recent Parental Brain conference highlighted emerging evidence that men’s brains also show signs of neuroplasticity as they become fathers.
“Mothers and fathers are frequently more similar than different in terms of how their brains respond to child stimuli,” says psychologist and professor
, who presented her findings earlier this month in Barcelona. “Instead of assuming that only women are hard-wired to parent, the science is telling us that all parents are equipped with a flexible, responsive brain that tracks with participation in care. Great fathers are made, not born.”It makes no sense to deny that men and women have biological differences — but it’s equally flawed to assume that only women undergo significant changes when a baby arrives. Saxbe’s research has found that fathers who are highly engaged and motivated showed the greatest decreases in brain volume. Interestingly, these same fathers — the ones who experienced the most grey matter loss — also tended to suffer more from poor sleep, depression, and anxiety than those with smaller brain changes.
Let’s be clear: when we talk about the brain “shrinking,” it doesn’t mean we’re becoming less intelligent (well, we may lose some intelligence, maybe, but let’s not blame the kids for everything!). This reduction in grey matter, which has been observed during pregnancy and early parenthood, is thought to represent a reorganization of the brain — clearing space for regions tied to empathy, enabling us to better focus on caring for our children.
“This might illustrate a cost of caregiving. The same brain adaptations that support parenting might also set us up for greater mental health risk. This doesn’t mean we should stop parenting, but rather that new parents may need enhanced support. Times of change are also often times of risk and vulnerability,” says Saxbe, with whom I had the chance to talk about this at the conference.
In recent years, studies of women’s brains during pregnancy and postpartum have expanded. Many show that some of the biggest changes occur in the default mode network — the system crucial for understanding others’ emotions and perspectives.
According to Emily Jacobs, a neuroscientist at the University of California, the “shrinking” of the brain during pregnancy is far from a bad thing — it’s more like pruning a tree. “It allows the brain to specialize more efficiently,” she says.
As with grey matter loss, “pruning” doesn’t imply loss in a negative sense. It’s the brain’s way of adapting — shedding what’s not needed to become more finely tuned for the job ahead.
Science journalist
unpacks this in her book Mother Brain: How Neuroscience Is Rewriting The Story of Parenthood, challenging the idea that women are innately, biologically programmed to be caregivers.“The story we've told about mothers is that women are natural, innate caregivers, that we come to this work automatically, that it just sort of springs forth from us as soon as a child is placed in our arms. And that it is really distinctly female, and that that's based in science,” Conaboy says. “And none of those things are true.”
More alike than we think
Before Saxbe’s talk in Barcelona, Spanish clinical psychologist and neuroscientist Susana Carmona presented findings from her pioneering 2017 study on how pregnancy alters the female brain — research that has only grown more comprehensive in recent years.
Her studies confirm that the brain changes in women who carry a pregnancy are more significant than in non-birthing parents or other caregivers. But it is now known that these changes are similar. Research by Carmona and Saxbe found that these changes are actually similar in nature across both mothers and fathers.
As it turns out, women’s pheromones — transmitted through skin contact and sweat — can lower testosterone and boost prolactin in men as their partner nears birth. This hormonal shift may dampen sexual desire but enhances neural plasticity, sharpens the father’s sensitivity to infant cries, and essentially prepares him to take on the role of caregiver. The drop in testosterone isn’t “good” or “bad” — it’s just a shift that better aligns men for nurturing.
One recent study showed that men whose testosterone levels dropped the most during their partner’s pregnancy — especially those whose levels synced with their partner’s — were better equipped for fatherhood. They formed stronger bonds with their partners and were more engaged in hands-on parenting.
Here’s the catch: while pregnancy triggers these changes in women automatically, in men they’re prompted by engagement. “A father’s brain changes — but it happens through his environment,” Carmona explains. “First by supporting the mother, and more importantly, through direct interaction with the baby.”
Learning as you go
All this left me thinking again about what it means to raise and care for a child. According to the State of the World’s Fathers report, 9 out of 10 parents say caring for their children is one of the most rewarding experiences of their lives.
The same report also finds that sharing domestic and childcare responsibilities more equally helps women re-enter the workforce, boosts kids’ cognitive development and academic performance, and leads to greater satisfaction and meaning for both men and women. It can also reduce stress — especially for mothers — and improve couples’ relationships.
Still, let’s face it: selling the “benefits” of fatherhood isn’t always easy. Getting involved often means giving up comforts, financial advantages, and even social status.
Some data: yes, today’s fathers are doing more caregiving than ever before — but mothers still shoulder more of the work in every care category.
When someone steps back from their career to raise children, society tends to treat it like a waste of potential — as if a title or paycheck is the only way to measure worth. Pursuing a high-status career brings public recognition; parenting, by contrast, brings deep but private joy.
Beyond the brain science, we’re far more complex creatures. Each of us is shaped by the interplay of biology and culture. “You learn to parent through trial and error,” says Carmona. She also warns against using brain changes as an excuse to make fathers more involved: “Fathers should contribute no matter what — we don’t need science to justify that.”
Connection is key
In a child’s first five years, the human brain grows to 90% of its adult size and develops about 80% of its cognitive capacity — laying the foundation for learning, behavior, and emotional well-being. So the real question is: where and how do we want to show up as fathers during that crucial time?
As the Parental Brain conference in Barcelona wrapped up, I joined a workshop with several of the scientists who had spoken in the days prior. In a casual conversation with Saxbe, we discussed the growing epidemic of loneliness among men — a trend that’s not just limited to the U.S.
There’s growing consensus that loneliness is harmful to health. One study found that socially isolated individuals are 32% more likely to die prematurely.
“The biggest question I get asked by fathers is how to find connection and friendship,” says
, father of three and author of The Ultimate Stay-at-Home Dad. “The lack of meaningful connections is a hole in our lives.”Saxbe agrees: men need connection — and children can be a powerful source of that. In today’s loneliness epidemic, men face more isolation and its consequences, including shorter lifespans than women. Building a close, meaningful relationship with a child can bring purpose and help combat that sense of emptiness.
From this perspective, embracing fatherhood isn’t just the best thing we can do for our kids and our families — it’s also a deeply human act that helps us thrive. It might even make the sleepless nights, the demands of fatherhood and the smaller brain volume feel worthwhile. Because caregiving shouldn’t be seen as a bonus — maybe it’s time we treat it as a mix of right, responsibility, and privilege.
That’s it for today. Thank you very much to those who keep sharing this newsletter, subscribing and writing to me (you can always do it by answering this mail, I answer everything!).
I love it when you send me suggestions or complete, criticize or correct some idea. I also love it when you share your own experiences. From the bottom of my heart, thank you so much.
You can find the archive of all the past editions of Recalculating here.
If you want to give me a hand, it helps me a lot if you “like” the publication (it's the little heart that appears there) or if you share it with someone (a thousand thanks to all of you who have been doing it! 😉).
You can also post it on social networks and follow me on Instagram (@nachopereyra23), Twitter (@pereyranacho) or Facebook (Nacho Pereyra).
With love,
Nacho
🙏 Many thanks to Worldcrunch for translating and editing this newsletter.
Before on Recalculating:
Shadows over childhood
Sometimes I catch myself thinking certain things no longer happen — left behind in the hazy past of my childhood. Like parents fighting at kids’ games. It’s something I saw a lot growing up around football in Buenos Aires, and, naively, I thought it had become a thing of the past (or at least has become quite rare).