You know fathers with smaller testicles react harder in the brain when seeing their babies. They also get rated as hands-on dads by their partners. Weird, right.
Of course you didn’t know this. Most people don’t.
These are just two of the strange, hard-to-believe details inside Darby Saxbe ’s Dad Brain. Saxbe is a psychologist at USC. She studies parenting. She admits upfront it feels a little odd for a woman to write the whole book on fatherhood. Then again, it hasn’t stopped men from writing entire libraries about women’s health.
She makes her point early. Engaged dads make families better. It affects the kids. It affects the partners.
Biology meets Culture
Saxbe wasn’t born into perfect family science. Her parents divorced. She watched her father plunged into solo parenting during custody days. She uses that history as an anchor.
The rest is hard data. Neuroimaging papers sit next to ethnographic fieldwork. The contrast is stark. Take the Aka people in the Republic of the Congo. Their dads carry infants in their arms nearly fifty percent of the time. They hunt and climb trees with the babies right there. Arm’s reach. Always.
Now look at the Kipsigis in East Africa. There, men believe baby poo and vomit can destroy their masculinity. So they stay away for weeks. Can’t even look.
The world is wildly inconsistent on what a father is. But the scientific record barely notices. Search for “mothers” and you get ten times the hits. “Fathers”? Ghosted.
The Invisible Patient
This invisibility shows up in hospitals. A premature baby goes to intensive care. The mother is recovering. They are both patients. They are tracked. Monitored.
The father wanders. Maybe he is in shock. He watches the birth. He sees the trauma. But he isn’t in the system. Nurses don’t check on him. Doctors forget he exists.
It doesn’t have to be this way. Involved fathers help kids sleep less often at night. They support mental wellbeing from day one.
Saxbe points out a weird trend: some online posts claim kids hit “peak oxytocin” cuddling moms, not dads. She dug up the source. The study never even measured oxytocin in the children. It looked at the adults.
She calls this out. It’s easy to oversimplify. Dads don’t just play. They soothe.
The Narrative Drag
Is Dad Brain perfect? No.
Saxbe jumps around a bit. She watches her dad. Then she talks about brain scans. Then she talks about cultural practice. It feels scattered. Like a collage instead of a line.
Also. Most of the science relies on heterosexual, two-parent couples. Saxbe tries to widen the lens. She touches on gay fathers. Trans parents. Step-parents. Adoption.
It’s not enough. The book is still overwhelmingly centered on the traditional unit. She tries harder than the literature does, but the data lags.
Still. It matters.
We give new moms so much space. Lucy Jones talks about matrescence —that intense shift in identity. It’s real. But dads shift too. The book argues they deserve attention. Not just because it’s fair. Because the brain changes. Because the child changes.
Because maybe, just maybe, we could stop pretending fathers are invisible until it’s too late.
