Daddy brain: how parenthood changes men

Can a shrinking brain and drop in testosterone levels ever be a good thing? Turns out, yes. We find out why fatherhood forces these neurobiological changes in men, and how they help our species survive. Plus… can the size of new fathers' testicles tell us something about their involvement in parenting? Guest: Darby Saxbe, PhDClinical psychologistProfessor of Psychology, University of Southern CaliforniaAuthor, Dad Brain https://www.darbysaxbe.com/dadbrain Credits: Presenter/producer: Sana QadarSenior producer: James BullenProducer: Rose KerrSound engineer: Roi HubermanTo explore more great episodes from the award-winning psychology podcast All in the Mind with host Sana Qadar, download the ABC Listen app (Australia) or search 'ABC All in the Mind podcast' wherever you get your podcasts. There you'll find more episodes on mental health, trauma, attachment theory, wellness hacks, and family relationships. You'll also hear interviews with experts like Esther Perel, Billy Garvey and Ethan Kross. All in the Mind is created for ABC's Radio National by specialist journalists and reporters at the Australian Broadcasting Corporation.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

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• 0:37Speaker 04

  Before the divorce, my mom's kind of chief complaint was that when she was in charge of the bedtime routine, he was hiding in his study.

• 0:47Sana Qadar?

  As far as fathers go, Darby Saxby's father was a fairly typical 1980s American dad. He was loving and fun, but not exactly very involved in the hard and annoying parts of parenthood.

• 1:00Speaker 04

  He always had these kind of hobbies that he liked to do on his own. And he just wasn't kind of as hands-on with the day-to-day, you know, getting us into the bath, getting us into bed.

• 1:10Sana Qadar?

  Then the divorce came. And initially Darby's father got sole custody.

• 1:16Speaker 04

  He was alone with me and with my two brothers. There was definitely a learning curve and I, you know, I think he sort of had to like fly by the seat of his pants a little bit to figure it out. And it didn't help that my brothers and I were pretty rambunctious, disobedient kids.

• 1:32Sana Qadar?

  But over time, her father started to get the hang of the day-to-day parenting thing.

• 1:37Speaker 04

  And so I watched him go from pretty typical 1980s dad to a really sort of like key parent and was wrangling all our homework, you know, he was the one, if we ripped our jeans, he was sewing patches on them. He was our chief chauffeur. Ultimately, my parents worked out joint custody, so we were switching back and forth every week. But I kind of came to see my dad as in some ways, the more stable and predictable parent because he just had a very calm set of routines that I appreciated as a teenager. And so I've always been interested in families and in fathers in particular, and how the fatherhood role changes.

• 2:17Speaker 04

  And I think one thing that is interesting about fathers is how different men's participation in parenthood can be across different contexts. And so thinking about what determines fathers' participation and how that's shaped by culture and society and norms and religion and love and expectation, I think gives us this really complex picture of how men opt into parenthood and how it then transforms them.

• 2:50Sana Qadar?

  Darby Saxby is now a clinical psychologist and a professor of psychology at the University of Southern California, where she researches families and fatherhood.

• 2:59Speaker 04

  Research is me-search. That was always the joke in grad school, like people study the things that they want to figure out in their own lives.

• 3:06Sana Qadar?

  Today, we're covering dads, their brains, their bodies, their mental health, because Darby has just written a book called Dad Brain: The New Science of Fatherhood and How It Shapes Men's Lives.

• 3:17Speaker 04

  We also see neurobiological changes in men when they become parents. And that tells us that parenthood is not just something that moms are designed to do.

• 3:28Sana Qadar?

  There's also a bit about testicles and testosterone in there.

• 3:32Speaker 04

  And they scooted the men down in the scanner and they also took images of their testicles. And then they linked men's testicular volume with their brain patterns.

• 3:43Sana Qadar?

  This is All in the Mind from ABC Radio National. I'm Sana Qadar. Today, dad brains, dad balls and the division of labour. You can't say we don't keep you guessing here on All in the Mind.

• 4:04Sana Qadar?

  There have been so many headlines in the last few years about the fact that, you know, the birth rate is falling, people are having fewer kids around the world. And for a lot of people, that's increasingly a personal choice. For others, you know, it's the result of infertility or a choice forced by economic or, you know, political circumstances, other circumstances. So that's kind of the context we're in right now. And given that's the context, I wanted to know, what was your aim with this book at this point in time?

• 4:29Speaker 04

  Yes, so, I mean, I think the falling birth rate is, like you said, a very multi-determined phenomenon. And my attempt here wasn't necessarily to try to diagnose it or to solve it, but rather just to look at the transition to parenthood as a transformative window of time in adulthood. So we think of infancy and early childhood as huge periods of development for children. We don't necessarily think of becoming a parent as a period of development for adults. And also expanding that window to include fathers, because so much of the child-parent research literature has focused exclusively on moms. And I think fathers are really interesting. They're really variable.

• 5:13Speaker 04

  And yet we also see neurobiological changes in men when they become parents. And that tells us that parenthood is not just something that moms are designed to do biologically, it's something that men have aptitude for as well.

• 5:31Sana Qadar?

  Darby's own dad had plenty of aptitude. It just didn't come online until after his divorce. He's told her in the years since that having to take care of his kids is the thing that kind of saved him.

• 5:43Speaker 04

  As hard as it was for him after the divorce, he was really sad. He felt like having to take care of us was the thing that kept him going. And that, it was really powerful for me as an adult to hear that, because I had always kind of felt bad that he was stuck with us. And instead he was saying, this was really like my saving grace, how much I enjoyed you guys and appreciated being a parent.

• 6:08Sana Qadar?

  It's interesting, reading your story and hearing what your mom said about, you know, the fact that she was doing all that kind of stuff and that was part of the reason for the divorce. That feels like a story that I still hear today, like that, that is like a precipitant to a lot of relationship breakdowns in families these days. Some things never change, I suppose, or some things do.

• 6:28Speaker 04

  Yeah, these are perennial issues. I think my mom was kind of ahead of her time. She was a doctor. She had a busy job. She was figuring this out with my dad. And now I think with even more women in the workforce, even more working moms, these issues are sort of even more on the table.

• 6:47Sana Qadar?

  Okay, I want to move on to talking about dad brains. And you've done a lot of studies looking at dad brains. So you've scanned the brains of dads pre and post baby's arrival. I want to know, what differences did you see in the brains?

• 7:01Speaker 04

  Yes, so we do see changes across the whole brain. And I always have to caveat that because people think it sounds alarming, but the brain actually shrinks. So it is losing grey matter volume, which in the dads that we scanned represented about 1% of their cortical volume. The cortex is kind of the top layer of brain tissue that contains a lot of our neurons. And so this kind of shrinkage of the brain, you know, it's, it's small, but it reflects what is likely a kind of remodeling to enable greater efficiency. So we also see the brain is losing volume at other periods in the lifespan, like, you

• 7:45Speaker 04

  know, when young children are losing brain volume as they kind of learn and grow and get ready to enter school.

• 7:51Sana Qadar?

  Right, like sign-ups or pruning kind of thing.

• 7:54Speaker 04

  Exactly, like we're kind of building these informational pathways that can help us process information more quickly. And that idea of that shrinking being adaptive is supported by the observation that where we see some of the biggest remodeling is in what we call the mentalizing brain, which are the pathways that help us think about other people's minds and gauge other people's intentions. And so those are pathways that are getting a lot of exercise in early parenthood. We're sort of imagining the intentions of a young child who can't communicate clearly with us. And as we're practicing working those circuits, they start to work more efficiently and we

• 8:37Speaker 04

  don't need as much brain tissue to do that work.

• 8:43Sana Qadar?

  Are those sort of the same changes that happen in moms' brains? Because moms need to mentalize as well.

• 8:48Speaker 04

  Yeah, exactly. So you see more profound changes in moms' brains. You see changes across more of the brain, but the pattern of change is exactly the same.

• 8:57Sana Qadar?

  Okay.

• 8:57Speaker 04

  So women are also losing gray matter volume across the transition to motherhood. In some of the studies of moms, the total volume change is more like 2.5%. So it's larger than what you tend to see in new dads. And it's also a little more across the board. So in our sample of dads, we saw a lot of variability. Some dads showed bigger brain change than others. And in our study, it was tied to the extent to which dads were participating in childcare. So when dads were spending more time with the baby, they were also showing greater brain change.

• 9:35Sana Qadar?

  But Darby says the way to think about this is that rather than there being a father brain and a mother brain, there's a parenting brain or a care brain.

• 9:43Speaker 04

  And it comes online in men, depending on the extent to which they're participating in childcare and they're kind of learning their babies, right? That social brain is getting more exercise and that's calibrated to their investment in their kids. So I think it's sort of like this brain that comes online. Men are primed to adapt, but whether or not they show those brain changes depends on their behavior.

• 10:10Sana Qadar?

  The bad news is these brain changes can also be a double edged sword.

• 10:14Speaker 04

  Exactly. So my lab found that the same brain changes that were linked with dads telling us that they were more bonded to their babies, more involved in care, doing more of the primary care, those same changes were also linked with dads telling us they were having worse sleep, they were having more symptoms of depression, they were having more anxiety, and they were having more overall psychological distress. And I mean, my take on that is just that, you know, we've long known about postpartum mental health risk in new moms, right? Like the transition to parenthood is kind of this time of opportunity, but it's also a time of vulnerability. And so to the extent that we're remodeling to prepare for parenthood, that is very adaptive

• 10:58Speaker 04

  in some ways, but it can also just create some new risk factors.

• 11:03Sana Qadar?

  So what should we take away from a finding like that then? Should dads not be over involved in the parenting? What's, yeah, what's the upshot?

• 11:11Speaker 04

  Yeah, I think the wrong message to dads is to say parenting is hard and risky, so don't do it.

• 11:16Sana Qadar?

  Yeah.

• 11:17Speaker 04

  Rather, I think we need to think of it as a public health problem, which is to say, how do we invest in having thriving kids? And knowing that both new moms and new dads can be vulnerable and that it's a time of really profound neurobiological remodeling, I think underscores the case for making real investment in this period, whether that's through generous parental leave, making sure that parents are getting other forms of support, the ability to be flexible.

• 11:52Sana Qadar?

  Okay, we've talked a bit about the brains of dads. I want to move on to talking about the testicles of dads because researchers have also scanned the testicles of new dads. Tell me about this. Why, what's going on here? What did they find?

• 12:06Speaker 04

  Yeah, this is one of my favorite studies because it always makes me laugh. So this was done by Jim Reiling, who is a researcher at Emory, who, whose work I talk about in the book. And, and he's been a real pioneer in looking at men's brains and, and how they change with parenthood. And so he did this study where they scanned men's brains that were responding to images of babies and, and also attractive women. And then they scooted the men down in the scanner and they also took images of their testicles. And so they were able to measure testicular volume. And then they linked men's testicular volume with their brain patterns in such a way that

• 12:46Speaker 04

  they were kind of able to make a link between men's reproductive strategy, which was kind of represented by the testicle volume, and their brain activation to kind of either sexual partner stimuli or caregiving infant stimuli. And there's this kind of larger theory among evolutionary psychologists that our brain and hormones reflect whether we're doing more of a kind of meeting oriented strategy where we want to maximize the quantity of reproductive opportunities that we can get. We're trying to get out there and get as many sexual partners as possible.

• 13:26Sana Qadar?

  I love the euphemisms you're putting on this.

• 13:28Speaker 04

  Yeah, I'm like, I don't know. Yeah.

• 13:30Sana Qadar?

  Very academic language for sleeping around while you've got a baby at home.

• 13:33Speaker 04

  Exactly. Sleeping around, quantity oriented strategy or more of a quality oriented strategy, which is to say that maybe we're just going to have a couple of kids, but we're going to invest a lot of time and energy and resources into making sure that they all survive and thrive. And men will undergo changes in their reproductive strategy as they move across the lifespan. So in, in the youth of a man, he might be more focused on quantity and opportunity. And then when he settles down and maybe enters a secure partnership and starts having children, he might be more focused on quality.

• 14:13Speaker 04

  But those strategies vary across cultures and across contexts, which is why I think trying to kind of link them to markers like brain activation or hormones like testosterone can be so interesting.

• 14:27Sana Qadar?

  And so the finding was, I feel like a middle schooler, but this is making me revert to my middle school self, like the bigger the balls, the more prone they were to not focusing in on one baby, like, you know, their baby and their partnership and sort of roaming around.

• 14:42Speaker 04

  Basically, yes.

• 14:43Sana Qadar?

  And so do we know anything about why certain dads had bigger testicles and so were behaving this way? Like, you know, what do we know about? What does this tell us?

• 14:52Speaker 04

  Yeah, I think it's, it's hard to tease out cause and effect a lot of the time because a lot of these things are measured at the same time. And so we don't necessarily know, but we're trying to infer, you know, that men's biology is driving something about the way that they are activating in response to baby cues.

• 15:13Sana Qadar?

  From ABC Radio National, this is All in the Mind. I'm Sana Qadar. Today, how the brains of men change in the transition to parenthood and what else is going on in the body, like with testosterone?

• 15:28Sana Qadar?

  So this brings us to testosterone, which there has been so much discussion in podcasts and online about the fact that, you know, testosterone does drop when men become parents, which, you know, for some is a point of freak out because there's a bit of an obsession with tea right now, especially in American politics and the elements of the menosphere. And so I imagine there would be some people who might take this finding to sort of prove that men shouldn't be involved in active childcare because it affects testosterone levels. So unpack what actually happens with testosterone and how we should potentially feel about that.

• 16:05Speaker 04

  Yeah, so I, I think the testosterone discourse in this, in the United States has definitely kind of entered a fever pitch. So, you know, for example, Pete Hegseth, who's our Secretary of War, recently announced they want to screen all military service members for their levels of testosterone.

• 16:23Sana Qadar?

  Yeah.

• 16:23Speaker 04

  So the idea that it's sort of this important feature that needs to be monitored if you want to be part of the US military. And, and yet I think this reveals a somewhat shallow understanding of hormones and how they're supposed to work. So our hormone levels should support our social roles and our social goals. And so what we know about the testosterone literature is that testosterone is often high in men before they become parents because they're seeking a mate. And testosterone is going to enable them to kind of compete and seek status and do the things that kind of, you know, support them in their quest for a mate.

• 17:06Speaker 04

  But after mating has been accomplished and it's time to focus on nurturing, testosterone naturally drops. And so longitudinal studies typically see lower testosterone levels in partnered men with children compared to single men, for example. And this is adaptive. So it is helping men contribute to being nurturant members of the family and invest in their partnership and their children.

• 17:37Speaker 04

  It's a good thing. So this idea that we want to be kind of maxing out testosterone to the highest possible level all the time doesn't actually fit with what we know about health across the lifespan, which is that having high-quality social relationships is a really important predictor of our wellbeing and our longevity. We should be thinking about relationship health and not just about testosterone as kind of a metric of health. So I should say, like, when testosterone is medically low, it makes sense to intervene. And, you know, you don't want testosterone levels to crash all the way down, but kind of normal dips in testosterone, right? So fluctuations in testosterone that match

• 18:22Speaker 04

  our goals and strategies that might change as we age and move into different roles. Like, those normal changes are part of what it means to be a healthy person, and we want to celebrate that flexibility and that adaptability, rather than feel like, no, no, no, we need to be supplementing so that testosterone is always sky-high.

• 18:44Sana Qadar?

  Yeah, I think that's a really great nuance that you inject into this conversation, because you're right, there is this prevailing kind of idea right now that low testosterone, low T equals bad all the time. And so if parenting potentially is going to lead to lower T, then you should maybe think about what the role of women versus men is. Like, there's a really kind of fever pitch conversation out there, as you said. Do you find people are being receptive to the nuance you are injecting into this about the role of testosterone over the lifespan?

• 19:15Speaker 04

  I hope so. I mean, I think it's always a little hard to know, but I mean, I think people understand that, for one thing, you know, as many doctors will say, maintaining high levels of T is costly to the immune system. So it comes with some downstream health consequences. It even suppresses men's sperm count. So, you know, there are these downsides to having high levels of T.

• 19:41Sana Qadar?

  That's very counterintuitive.

• 19:42Speaker 04

  It is very counterintuitive. So it's ironic to think that the same people that are saying they want more babies to be born are also saying that men need to be supplementing testosterone to kind of achieve peak health.

• 19:53Sana Qadar?

  Yeah.

• 19:54Speaker 04

  So I really think we need to broaden our understanding of what health looks like. I talk about this in the last chapter of the book, but, you know, being part of a sort of connected community and having a family, having a support system, all of these things are linked with longevity and wellbeing in late life. And so, you know, if we're sort of thinking high testosterone equals health, the story has a lot more nuance to it. There's, you know, more subtlety that we need to consider.

• 20:29Sana Qadar?

  You have a chapter in the book called "A Crisis for Couples," and we kind of touched on what this crisis is when we talked about your family's personal story. But tell me about this crisis that hits couples when they have a child.

• 20:42Speaker 04

  Definitely. Yeah. So there's some evidence that across a whole host of different studies, that when couples welcome a new baby, it tends to accompany a drop in their relationship satisfaction. And it makes sense if you think about all the stressors that can accompany new parenthood. So, you know, soon-to-be parents are often at a peak in their relationship satisfaction before a baby's birth. They're excited to have a new baby. And then, once the baby arrives, there are new financial pressures, there are time pressures, there's sleep deprivation, there's new conflict around roles, who's going to do what. And

• 21:23Speaker 04

  so, you know, we see a lot of couples will report kind of more distress after the transition to parenthood than they felt before in their relationship.

• 21:32Sana Qadar?

  Yes, this is something I've definitely seen in my personal life. I've seen it in many other young families. But you write about the fact that, you know, there's a difference between the kind of immediate fall in the enjoyment you're getting out of life versus the longer-term wellbeing benefits you reap from parenthood. So tease apart sort of those differences.

• 21:52Speaker 04

  Yeah, exactly. So there are a lot of time diary studies that find if you just ask people moment to moment, kind of, how much fun are you having? How happy are you? Parents will often report lower moods than non-parents. So they'll say they're more stressed, they're having less of a fun time. But if you kind of zoom out and you ask people, does your life feel meaningful? Are you satisfied or content with where you are? Do you feel like you have a sense of purpose? Oftentimes, parents will endorse more of those feelings. And so in psychology, we have these kind of nerdy terms, eudaemonic wellbeing, which is that sense of longer-term contentment, having a sense of a place in

• 22:37Speaker 04

  the world that you feel good about, versus what's called hedonic wellbeing, which in the book I say it's like sipping a pina colada on the beach kind of wellbeing. It's like, you know, having fun in the moment, things that seem, you know, going on vacation, having an ice cream sundae, things that are pleasurable. Parenthood is a little low on hedonic wellbeing, but it can be really high on eudaemonic wellbeing. And it's that eudaemonic wellbeing that is really often tied into what makes us happy in the long term, not just kind of what gives us pleasure moment to moment.

• 23:13Sana Qadar?

  Okay, that's going to have to be my new parenting mantra. You're working on your euda... Oh, my God, I can't even say it. Eudaemonic?

• 23:19Speaker 04

  Eudaemonia, eudaemonic wellbeing.

• 23:22Sana Qadar?

  Eudaemonic wellbeing is what I'm working on.

• 23:25Speaker 04

  It's a Greek word.

• 23:26Sana Qadar?

  Not necessarily my hedonistic wellbeing.

• 23:29Speaker 04

  Exactly.

• 23:34Sana Qadar?

  And in terms of, like, surviving that acute period of time after children arrive where things aren't so great, how much does working on division of labor play into that? Because, you know, a lot of the bickering and a lot of the loss of enjoyment in day-to-day life is there's just so much crap to do, and usually one person kind of, it gets lopsided a little bit.

• 23:56Speaker 04

  Yeah, exactly. You have all these kind of annoying things to do, whether it's waking up with the baby, to feed them in the middle of the night, or changing diapers. And so there can be a lot of kind of squabbles about whose turn it is to do what. And in my lab, we looked at this. We gave couples a checklist of 10 baby care items. When they were pregnant, they came into our lab and they did this discussion. We called it a who does what, where they told us, here's how we plan to divide up these tasks. And then, when the baby was about six months old, they came back to the lab and they had that discussion again, and they filled out that same checklist again to say, here's what we're actually doing. And we found that couples were pretty bad predictors of what their division of labor was going to be. In pretty much every case, couples thought the dad was going to

• 24:41Speaker 04

  be doing more than what he was ultimately doing after birth. And dads especially kind of expected that they would do more before birth and reported that they were doing more after birth than moms did. And so there was that sort of like dispute even within couples in terms of who was doing what.

• 24:59Sana Qadar?

  And what do we know about men's satisfaction with parenthood and their lives when they are more involved in parenting, whether it's doing more of the equal load of work, or, you know, yeah, being a very present father?

• 25:13Speaker 04

  Yeah. So in that particular division of labor study, we actually found that when men were telling us that they were doing more of the baby care after birth, they were reporting lower parenting stress, and the couple was reporting better satisfaction. So you might think that men would get a benefit from doing less because they have more time to relax, but it was actually the men that were more hands-on that were feeling like they were enjoying parenthood more. So, you know, I think there is some value in dads just kind of getting in there and developing some confidence and a comfort level with baby care. And in terms of like, sort of the broader picture of what does parenthood

• 25:52Speaker 04

  do for a man's wellbeing, you know, again, sort of going back to that idea of long-term eudaemonic wellbeing, some of the biggest longitudinal studies we have, like one that's been done in the US that spanned over 80 years, is called the Harvard Grant Study. It's a, it's a study where men were recruited as 20-somethings and followed into their 90s. And they found that more than their bank accounts, or really any other characteristic of their physical health, it was the quality of men's relationships, like the men who were in satisfying marriages, the men who felt good about their relationships with their kids. Those were the men who had the greatest wellbeing later on in life.

• 26:41Sana Qadar?

  Then to finish, if we take an eagle-eye view of the research that's out there, for those who want to be a really great dad, what are the key factors or behaviors that they can make sure they're doing to enable that?

• 26:54Speaker 04

  Yeah. I mean, I think all our research points to this idea that the brain and body adaptations come online when dads are more involved in care. So I think that's, you know, hopefully encouraging to dads that it's not that their biology isn't priming them to be good at care. I think a lot of men sort of come into parenthood with that assumption that they're going to be behind, or that they'll be hapless in some way, that their partner's going to have more of a knack than they will. And instead, it's really about practice and repetition and kind of getting experience. Those are the things that shape the brain and the body and help us to become more sensitive and empathetic caregivers. So I would say for men who are reluctant, just get experience, right? Like,

• 27:36Speaker 04

  the more you learn your own baby, the more expertise you have. You know, the more diaper changes you do, the more play sessions you take over, not only will you get to know your baby better, but you'll enjoy your baby. So, and I would also say, like, there isn't any one window in which to kind of jump in and be a hands-on dad. Like, dads can make great contributions to kids' lives at all different ages. So, you know, stay involved and keep communicating with your kids because they need you and they'll benefit from your involvement in their lives.

• 28:09Sana Qadar?

  That's like your dad. He became a much more hands-on dad when you were older, and it still made a huge difference.

• 28:14Speaker 04

  Exactly. I think of him as one of the most important figures in my life.

• 28:21Sana Qadar?

  Darby, thank you so much for chatting.

• 28:22Speaker 04

  Thank you so much. This was really a great pleasure.

• 28:27Sana Qadar?

  That is Darby Saxby, professor of psychology from the University of Southern California. Thanks to producer Rose Kerr and senior producer James Bullen. Our sound engineer this week was Roi Huberman. And that is it for All in the Mind this week. I'm Sana Qadar. Thanks for listening. I'll catch you next time.