The Science of 'Dad Brain' | Darby Saxbe (Mom of 2, USC Professor & Researcher)

StartupDad_DarbySaxbe Final Transcript

Darby: This is really cool to study dads because they're more plastic, there's a lot of variability in how they show up as parents. We also know that although they're not pregnant, their hormones can change during a partner's pregnancy and in the early postpartum months as well.

So what is that going to look like in the brain?

Adam: Welcome to Startup Dad, the podcast where we dive deep in the lives of dads who are also leaders in the world of startups and business. I'm your host, Adam Fishman. Today was a unique conversation as I sat down with Darby Saxbe, a startup mom. She holds a PhD in clinical psychology and is a professor at USC.

Her research includes studying the effects of stress hormones in couples. And most importantly, The changes that the male brain undergoes after becoming a parent. She has scientifically discovered something she's termed “dad brain” and is in the process of writing a book about her research. She's also a mom of two kids.

In our conversation today, we spoke about early influences on her scientific research, what it was like having two kids while getting your postdoc, and the neuroplasticity of the brain. We dove deep into her research in a very approachable way and I learned about stress hormones in couples, how fatherhood reshapes men's brains to make them more efficient, and changes in something called the default mode network and the visual network in new dads.

We also covered how brain changes are different in new dads versus new moms and what the implications of her research are for public policy, paid family leave, and the support for new parents. I've never learned more in a conversation that I did with Darby, and I hope you enjoy it as much as I did.

Adam: I would like to welcome Darby Saxby to the Startup Dad podcast. Darby, I'm excited for this conversation. It's going to be a different one that I typically have on the show. Welcome.

Darby: Happy to be here. Thanks for having me.

Adam: So Darby, you are not a dad, but you've done a lot of studying of dads. And so I wanted to kind of just get into why I invited you on the show. You're a researcher and a scientist and curious to just hear more about your professional background and the areas of research that you specialize in.

Darby: So I am not a dad, but I'm a big fan of dads and I've been studying dads now for about 10 years in my lab as part of a larger set of studies on the transition to parenthood. And I think that dads are really interesting because they don't experience pregnancy directly. And as such, they can teach us a lesson about how parenting experience shapes the brain and body kind of above and beyond just the hormonal changes that are wrapped up in pregnancy, birth, breastfeeding, all of the kind of biological events that biological mothers undergo.

So I got interested in this area you know, through a series of kind of lucky coincidences. In graduate school, I was studying cortisol patterns. Cortisol is a stress hormone, which I think we'll talk about at some point today. Cortisol patterns in couples with children, who the families had older children and I was interested in looking at how the cortisol patterns were connected to each other and what factors were changing the kind of stress system in the families. And that got me interested in looking even earlier. So before your kids are older and functioning independently, what about babyhood?

And then even earlier, what about pregnancy? What about that transition? So looking from when the couple, the dyad becomes a triad, just seemed like a really interesting juncture in, the kind of transformation of a family system. So that's how I got into transition to parenthood research. And then I think fathers are just really understudied and really interesting.

And in some ways, because they're more variable than mothers typically, in the sense that you have fathers who have never met their child ever. And you also have fathers that are primary caregivers. You have this really wide kind of gamut of different levels of engagement and motivation. A lot of that is mediated through culture and society.

So, I think fathers are just really fascinating to focus on.

Adam: Cool. Well, I'm excited to talk about that with you today. Now I also read, I did some research for this. You probably would be proud of me researching and reading your stuff. And by the way, I found it super approachable. Like I am not an academic. I mean, I did go to college and I have some academics in my extended family, but I found the research fascinating and super approachable.

And I'm definitely going to link to some of it in the show notes. But I also read that you started your scientific research journey in seventh grade, studying handedness and its impact on visual fields. Fun fact, I also did a science project on handedness because I'm left handed and I built a device to keep people from smearing the page when they write. But was that, was the, your seventh grade handedness study, the spark of your scientific journey, or were you kind of drawn to this path even before that?

Darby: Yeah. First of all, I'm impressed that you did that deep of a dive that researched my seventh grade science fair project topic. I think that's probably the most impressive interviewer level of research I've ever gotten. But I think it's like a joke in the psychology, clinical psychology world that research is me-search like..shy people study social anxiety you know, people with divorced parents like me are interested in couple relationships. You always worry about the person that's studying severe mental illness. But as a left handed person, I was always kind of curious, you know, there were sort of pillows and posters that said things like, you know, I'm in my right brain and other people are in their left brain.

And so that just sparked my curiosity. Like, is there something that might be different about my brain as a lefty? And so I read a book that was called left brain, right brain, and, you know, kind of based a project on that. But it was the first time that I ever read about neuroscience research or neuroimaging, or the idea that you could like look inside the brain.

And this was the 80s, so the field was in a pretty kind of primitive, nascent place, but it still just seems so cool that there was technology that would let you see what the brain was doing. So, I then went to college as an English major, which was a little bit of a switch but I just love to read and I always enjoyed English classes.

And then kind of towards the end of college started thinking, I don't know what I'm going to do with this degree. And I added a double major in psych in part because of that initial spark of just, I really liked studying the brain and was curious about it. And then actually ended up working for a startup right out of college.

So I worked at an internet.com startup for a few years that did kind of media and community stuff. And then the stock market crashed after 9/11 and we all decided the internet wasn't going anywhere and nobody was going to make any money doing internet stuff. So I went to grad school. And that

Adam: As one does.

Darby: As one does. And then my third year in grad school, actually the company that I worked for the internet company sold for millions upon millions of dollars. And of course I had cashed in all my stock options at that point. So it was too late. But you know, if I hadn't done grad school, I wouldn't be here today.

So I think it all worked out.

Adam: Yeah, and also, you know, you're in the highly lucrative field of doing academic research, which I'm sure is just full of stock options and things like that. Right?

Darby: Yeah. People really do not go into it for the money,

Adam: Exactly.

Darby: But it's fun. So, you know,

Adam: I also read that you had two kids. Well, you have two kids, but you had them while you were getting your postdoc. And so one, that seems like an impressive feat to me. I sometimes cease to function when my kids need something from me. Definitely am not getting a postdoc while I'm growing two humans. Did that also shape your curiosity and interest in brain development and it sort of the impacts on parents and their psychology, postpartum?

Darby: Definitely. Yeah, I mean, going back to the research is me-search idea, right? So at this point, I'd been studying stress and couples and families. I'd been doing my dissertation research on families and stress and conflict and housework and, and then when I had my own kids, I thought like, this will be so easy.

I'm an expert. I know everything about families. And I was just like completely, you know, flummoxed by what it was like to, you know, try to work and have little babies and, you know, adjust to becoming a parent. So I thought, yeah, like this is a really big life transition for people. And there isn't enough research about it.

And yeah, to your question, like, was it hard? I was extremely sleep deprived, but in some ways, like the postdoctoral training period is a good one for academics because you're done with grad school. You don't have classes. I'm a clinical psychologist, so I had a lot of clinical work that I was doing in grad school. But you're not yet on the faculty, so you're not teaching. You're not mentoring. You're just doing pure research. So you have a lot of flexibility about where and when to do that. So, it was in a lot of ways a good time to have kids, but there's never an easy time when you're trying to be a researcher because you're always having to hustle to kind of keep your head above water in a competitive field.

Adam: Speaking of that research, I read that in one of your papers, and you mentioned earlier in our conversation this idea of cortisol patterns in couples, and you mentioned cortisol as this stress hormone. Can you explain a little bit more about that research, what cortisol is and what you observed in doing that research?

Darby: Yeah, totally. So yeah, cortisol is a stress hormone. It's actually the end product of the stress response that starts in the brain and then goes to the pituitary and adrenal glands. And cortisol is something that psychological researchers are really fond of because you can measure it fairly non invasively and easily in saliva.

Or blood or urine, but saliva is great because you can follow people around and you can have them sample their spit and you can link what you're seeing in terms of their cortisol levels to what they're doing, what kinds of relationships they're in. So I did a series of studies looking at cortisol patterns in dual income couples with kids.

And I was interested in how family stress might affect that sort of biological stress patterning. So the first study I did actually was my master's thesis. I found that for women who were less happily married, their cortisol patterns were less adapted, less optimal. So, they showed cortisol patterns that kind of looked like the patterns we see in people with burnout and chronic stress.

And we got that effect for the women in our study, not for the men which kind of dovetails with a lot of research about the importance of marital quality for women's health. And so I followed up on that with a few studies to look at, well, what was it about the relationship or about the household that might matter for stress hormones?

And we looked at division of domestic labor. We found that for both the partners both the husbands and the wives doing more housework is linked with worse patterns of cortisol recovery. So it turns out housework is bad for your health. And we also found that within the couples, their cortisol levels were linked with each other.

So, we know that when you're sharing space with someone, your emotions can be linked, right? And your thoughts and beliefs can become linked over time. But this was really the first study showing that in cohabitating couples, you can also see linkage in stress hormones, and that seemed like an exciting finding because it told us something about how marriage might affect health, how living with a partner might affect your health over time, if you're actually producing correlated levels of stress hormones.

Adam: So essentially, I mean, you did an amazing job explaining that, but if I were to dumb it down to like Adam level of the explain it like I'm five, basically, if I'm stressed, my partner is more likely to be stressed and vice versa. That's amazing.

Darby: It's funny, like I would have assumed that having stronger linkage, like having more correlated cortisol would be a good sign because it would mean the couple's more on the same page. But we actually found that the more unhappily married the couples were, the more strongly associated their cortisol levels were, seems like a stress contagion kind of finding that if I'm in a bad mood, if I'm stressed, the worst thing I want to do is transmit that to my partner.

It's much better if my partner can maybe help to modulate or is coming in with a different stress state. So that really sparked my interest in just looking at inner relationships between family members in terms of biology and physiology.

Adam: That's a fascinating study. Thank you for sharing that. I wanted to transition to talking about dads and dad's brains. Can you give us an overview of your research on how fatherhood affects men's brains? And then also why is this an important area to study?

Darby: So after doing the cortisol research and the research in couples, I was really interested in transition to parenthood as this time that seems like a lot was in flux. We know about our biology changes. We know our relationships are changing. And I wanted to add a neuroimaging component to the project to look at what's changing in the brain.

And so the initial impetus to look at dads was actually in some ways born out of convenience. Because my neuroimaging center wouldn't let me scan moms while they were pregnant. Right? Because you don't really want to put pregnant women in the scanner.

Adam: Is this in like an MRI scanner, like an FM functional MRI scanner or something?

Darby: Yeah, so it's in the MRI scanner at my university and it's essentially like a really big magnet and you're going inside the magnet and the magnet is looking at how blood flow is changing in the brain because the blood flow is kind of getting picked up on by the magnet. But you don't want to put pregnant women in a giant magnet unless you have a pretty good medical reason to do so. So I thought, well, I want to scan somebody. How about the dads? And then, you know, I had already done all this work on cortisol linkage within couples and relationship dynamics. So it actually felt like a very logical extension of what I was already interested in, which is how do we influence each other in social contexts? And then I started thinking. This is really cool to study dads because they're more plastic, there's a lot of variability in how they show up as parents. We also know that although they're not pregnant, their hormones can change during a partner's pregnancy and in the early postpartum months as well.

So what is that going to look like in the brain? So we started scanning men who were coming into the lab alongside their partners in mid pregnancy. And the scan took place as part of a larger visit where we also took saliva,we took hair, we took blood, we wanted to look at hormones. We had the couples engage in interaction with each other.

How did they feel about the pregnancy? How did their relationship look? And we scanned the dad. So this was our prenatal scan. And then we brought the families back when the baby was about six months old and we did the same kind of stuff. We got the hormones, we had them talk to each other. We had them play with the baby.

And we put the dads back in the scanner. So we wanted to see from prenatal to postpartum what looks different. And I should rewind a little bit and tell you why I was expecting to see the results that we ended up getting, which is that while we were halfway through data collection for this study, a big paper came out that was published by a research group in Spain that was looking at how women's brains changed over the transition to first time motherhood.

And in that study, they had recruited moms from a fertility center before they even got pregnant, and then followed them into the first few months postpartum. And what they found was actually that the brain got smaller. So it lost gray matter volume. Gray matter is the layer of tissue in the cortex that includes like the neurons, like the cell bodies of neurons.

So it's like the layer that's kind of important for our thinking. And there was shrinkage of this gray matter all across the brain, but especially in regions that are linked with social cognition, thinking about other people's minds. And the more the moms lost gray matter volume in the cortex and in other parts of the brain, the more they said they were attached to their babies after birth.

So it appears that losing volume is adaptive. It's supporting preparation for motherhood. And it may be that it reflects a sort of consolidation or streamlining of connections in the brain to make them work more quickly and efficiently. Right. So you hear like we're losing gray matter. That sounds really bad, but it's probably a remodeling that makes the brain work better.

And we actually see gray matter is lost in adolescence as well, which is a time of a lot of brain development and restructuring. As we mature, we actually lose gray matter. So that's helping us develop better. So that was all sort of to introduce that when I saw this study, was instantly really jealous cause I thought their data was really cool and I had a sabbatical coming up and I ended up writing a Fulbright grant proposal. The Fulbright is like a grant that. It sends you somewhere international to do research. So I wrote a Fulbright to go hang out with the people that published that study of moms.

And I discovered that they had a sample of men that they had also scanned alongside their partners. And so that Fulbright experience kind of yielded our first publication, which was 20 dads from my lab, 20 dads from their lab. And what we found is that the dads actually showed really similar patterns of gray matter volume loss from prenatal to postpartum that looked a lot like what we had seen in the moms, but the changes were less widespread, so they were in fewer parts of the brain, and they were less significant, they were, like, less pronounced, right? Which kind of goes back to this idea of, like, dads are interesting because they're variable. So I think with dads, we care about individual differences in parenting engagement, rather than just this overall change that all dads are going to show.

So the Spanish group found that in moms, the changes are so significant from before and after birth that a machine learning algorithm can actually tell the brains of mothers apart from the brains of non mothers, just by looking at the scans. 

Adam: Wow. 

Darby: It's harder to do that for the dads. So, I wanted to follow up on that and look within the sample that I had recruited in my lab, where, as I just told you, we collected all these other kinds of data.

How did you feel about the birth? How much time do you want to take off from work? How much time are you spending with the baby after birth? How do you feel about the baby? Right? We gave them so many questionnaires. So I wanted to see, like, are these patterns of brain shrinkage linked with what they're telling us on the questionnaires?

And they were. So it turned out if dads were more motivated they told us that they felt more bonded to the unborn baby before birth. They said, I want to take more time off. They subsequently showed more of that gray matter volume reduction in some of the same areas that we'd seen in the moms and the dads who showed more of that gray matter volume reduction also were spending more time with the baby in the first three months after birth, particularly more time alone as the primary caregiver.

And they were reporting stronger bonding. They were enjoying the baby more and they had lower parenting stress. So it seems like that pattern that we saw in the moms was tracking with the dads kind of motivation and involvement with the babies both before and then shortly after birth.

Adam: Wow. And so, you know, you mentioned that the moms were sort of more consistently, you saw that step function change, but then in the dads who spent more time, you saw more pronounced step function change. And so do you think the reason? I mean, I'm just sort of maybe leading the witness here a little bit, but it seems like the reason that it would be there with the moms is because of the, sort of the default mom spends lots of time with the baby. And what it sounds like, what you saw is if that is actually dad as well, then dad sees a very similar result. Is that, am I kind of a little accurate there

Darby: Yeah, no, I think you're very accurate. The one thing I would correct is just you said function, but this is actually brain structure. So structure and function are a little bit different. We didn't look at how the brain, like if I wanted to look at function, I would look at like, what's the brain doing when the baby cries, right?

This was more just like looking at like, how big is the brain? So we don't necessarily know anything about function, but we can kind of imagine that the function might change alongside structure. And that's something we're looking at in my lab. But yeah, I think there are a couple of reasons that the changes were so much bigger for the moms.

I think one is, like you said, there's just like a more socialized kind of cultural role for moms to be the primary hands on caregiver in the first few months, especially, right? And there was a little more noise in the sample of dads because some were spending a lot of time, some weren't spending as much time.

Some of that has to do with how much time do you get off from work? Typically moms take longer leave and have more time at home. The other piece of that I think is the hormone piece, right? So like I said, like men's hormones do change around the transition to parenthood, but it's hard to compete with like someone who's literally growing an entire human. You know, they're like crazy hormonal swings that happen as you prepare for birth that help to precipitate labor. You get this big surge of oxytocin that helps you push the baby out. And then, of course, if you're breastfeeding, right, you get a lot of hormonal changes associated with that. So we know that hormones can drive changes in the brain and it's possible that moms just had like a bigger dose of the hormones that might influence brain structure change. The third thing that I think we need to know more about that we don't know as much about as we should is sleep and like whose sleep is getting disturbed and to what extent is sleep loss contributing to this gray matter volume loss. So in the dad study that I just told you about, we actually did look at sleep problems and the dads who lost more gray matter volume also had more sleep problems. So I kind of think that the parenting piece is actually running alongside the sleep piece, and both are contributing to a reshaping of the brain.

Adam: So you've actually kind of proven out at least from a size of brain standpoint, the existence of mom brain and dad brain, and I know we kind of talk about. the concept of mom brain is like, oh, I'm more forgetful now. And that may or may not actually be true, but you've actually observed physical shrinkage in the brain.

And then I've read some articles where, you know, is dad brain a thing and it sounds like it is.

Darby: It sounds like it is. I mean, I should give the caveat, our sample was super small. So, you know, we had the original paper was 20 dads from my lab, 20 dads in Spain. So 40 dads altogether. That's not a lot of dads. And then my follow up study that I was telling you about where we looked at parenting engagement was 38 dads from my lab.

So these are tiny samples. The mom studies have somewhat bigger samples. In five years, somebody might publish the definitive refutation of all this research. That's always possible, but it seems like we are seeing these changes and what makes me feel more confident is that not only are the changes in men tracking with what we're also seeing in women, but they're also kind of consistent with what you see in like mammals, like in primates, in rodents, right? Like we know from animal models that parenting experience does change the brain and it changes our hormones. So it makes me think that this is a real phenomenon and it's not just something that we're like accidentally, you know, picking up on some kind of crazy noise.

Adam: Yeah. The concept of my brain shrinking after having kids is somewhat terrifying to me. It's a little too late to put that genie back in the bottle for me, but for you too. But like, is this something that a parent should be worried about? It doesn't sound like. There's a, like a worry or a health issue.

It just sounds like it is what it is. And this is a really interesting observation. How would I talk a few dads or potential dads, off of the panic that they're maybe feeling with

Darby: Yeah. I mean, I feel like the worst case outcome of this research, right, is that young men hear about it and think like, I never want to have kids because I want to keep my brain at its current size. And that would be really sad. Or if current dads start to think like there's something wrong with me, right?

Like this isn't a deficit model. I mentioned that the brain also loses gray matter volume in adolescence. Also, we lose gray matter volume in the first few years of life. So as we're starting to develop in infancy and toddlerhood, we are pruning and our brains are again, getting more streamlined, more efficient.

So our brain might get smaller, but actually function better, right? It's like, we become like a leaner meaner machine. So I think that's one argument. I think the other thing that we still don't really know, cause we don't have enough longitudinal research is like, what is the rebound or recovery look like?

So, like, we know, for example, that men who become parents, you see a dip in testosterone in early infancy, you know, when you're parenting a baby, but that there's often a rebound, right? And I suspect that similar things are happening in the brain. And in fact, There are a couple pretty new studies that I think are really exciting, not from my lab, but from, there's this huge, big, like pool of brains. It's called the UK Biobank. It's like thousands and thousands of older adult brains.

Adam: I have to say when I think about a pool of brains, my, my head goes to a very different place than I think yours does. I'm in zombie movies right now is where I'm at.

But, but I get you

Darby: You know how like Scrooge McDuck is always like swimming through the pool of coins. I don't know. It's I picture it like it's a repository. It's like all these brains, they've all been scanned. So you have tons of data from thousands of people, and they looked at if you had had more children, and in both men and women, having had more children is actually linked with what is considered to be a younger looking brain. So if you take the brain scan and you use machine learning to estimate its age, you know, it's like looking at someone who's had a lot of Botox, right? And you're like, are you 50 or are you 80?

It's like the brain looks younger among people that have had larger numbers of children. And that's true not just for moms. It's true for dads. It's true for men. And I think we don't totally know why that is like, again, it could be hormones, but it could also just be like enriched social experience.

And learning and cognition and maybe just having larger social networks, like we know that for men in particular, like social connection is actually really important for longevity and long term health. Like there's all that, like the Harvard grant study, which is this very longitudinal 80 year study, men who had richer social connections live longer and were healthier.

And so like parenting in some ways is a proxy for that. So my point is, like, it sounds scary that you could be losing some brain volume, but ultimately it seems like it's a neuroprotective thing to be a parent. And I should finally caveat that before you think about, like, the guy in Beetlejuice with the shrinking head, like, it's not like you're losing a huge amount.

It's like, in my study, it was about 1%.

Adam: Okay.

Darby: So your brain is probably going to look like a similar size, like to the naked eye.

Adam: Yeah. Yeah. I wanted to come back to one thing you mentioned, which is this sort of the brain sort of reshapes itself possibly to get more efficient. And one thing that comes up a lot in this show, and also when you talk to parents who are also working professionals and you're like, how do you get so much done?

And they're like, Parenting has been an amazing unlock for my focus and efficiency. I know I need to get N number of things done in Y amount of time. Cause I got kids to take care of and like, et cetera. So it's interesting that like, you know, I don't know that there's a direct tie to this, but this idea of like the brain kind of getting rewired a bit.

To make you more efficient and more streamlined to do the things you need to do in this next phase of life is pretty fascinating.

Darby: Yeah, I agree. I mean, you asked me earlier what it was like having kids as a postdoc, right? I would say like before having kids, I was always a night owl who was like, you know, working at midnight, keeping really bad hours, being procrastinating. And once I had little kids, like my body just couldn't do that.

Like I just couldn't stay up late because I would have to wake up the next morning. So I actually just had to be able to focus more and be more productive and efficient, work fewer hours, but work smarter, not waste time. Not to say that I don't like surf the internet all the time, but it's like, you know, I feel like I have become much more able to get things done very quickly.

So I totally agree with that idea that things change in a way that actually can often make us more productive in realms beyond just being a parent.

Adam: Yeah. There's two other things that I wanted to ask you around some of your studies of new dads. One is this concept of the default mode network and then the other one is another network, the visual network for new dads. And so I think I know what the visual network is. But what is the default mode network and what changes in a new dad?

What did you observe there?

Darby: Yeah so the default mode network is really cool, it's a fairly recent discovery. I would say like in the last, I mean, not that recent 15, 20 years. But a lot of neuroscience used to focus on what is the brain doing when I'm doing a specific task? Like, If I'm seeing a face of someone I know versus a face of a stranger, or if I'm sorting letters and I have to press the space bar when I hit the letter X, right?

Then in order to see what my brain is doing, I'm subtracting known face from stranger face. Or I'm subtracting X from other letters. There's always subtraction, right? Because we want like a baseline of what is the brain doing when it's doing a similar kind of task. And then we want to know about the specific effect of like, in the face example, familiarity or in the letter example, inhibition, right?

I'm like pressing or, you know, whatever the cognitive paradigm is. So, there was a neuroscientist who started to realize, like, we're always comparing one task to another task, or we're comparing a task to when the brain is doing nothing, and we kind of assume that the brain is just sort of empty, and when the brain is doing nothing, that's a good baseline for any kind of task.

It turns out when you're not giving people a specific task, the brain is actually really active. So that's why it's called the default mode, because it's like, what does the brain do when you don't tell people to do a specific thing? When I'm not looking at a face or I'm not pressing a letter, what is my brain doing?

So it turns out when people are just in the scanner without a specific thing to do, they end up daydreaming, they reflect, they think about their own memories, and a lot of the time they think about other people, right? Like you wonder about people in your lives. What's this person thinking? Why is this person acting this way?

So you engage in what we call like social cognition. And so for that reason, the default mode network, which is the sort of series of structures that light up when you're in the scanner doing nothing, is also called the mentalizing network. Because, It's the same series of structures that light up when you ask people to think about someone else's intentions or why is somebody doing the things that they're doing so you can activate that network when you show people pictures and you say, why is the person in this picture executing the action that they're executing?

So as soon as you start thinking about people's motivations, you're lighting up in that default mode network. So that's why we kind of think of it as like a social cognition network. And that was one of the networks that showed the biggest change in the studies of moms and also in the studies of dads.

Which makes sense because when you have a baby, it's almost like social cognition on steroids. Like you have to try to figure out what is this person that can't talk need for me. They're crying. I don't know why they're crying. Like I have to problem solve and figure out like what's in their environment that could be causing them to cry. So that I can fix it. So. It makes sense, right? That if you're getting efficient in one part of the brain, that would be the one you'd want to get efficient in. The visual network was kind of a surprise. That was another network where we saw changes in the new dads. And my best hunch about why that seemed to be dynamic is just that you need to use your visual skills to recognize your baby, to tell your baby apart from other babies, like if you want to be a good sensitive caregiver, you want to read your baby's emotional cues, see what their expressions mean. So again, it might be an adaptive network in which to kind of get more efficient.

Adam: That's amazing. I'm learning so much on this show today. Thank you. I wanted to ask you on that default mode network for dads, you mentioned, well, and moms, but you mentioned the social cognition and the sort of the baby's crying and you have to decipher what they mean. I've always found it amazing how parents, myself included can then sort of like detect the type of cry and a non parent might hear it. And it's like, it's all the same thing. But I wonder if that has something to do with the enhancement in social cognition that comes that you observed, at least physically in the default mode network with new parents.

Darby: Definitely. You know, there's some really interesting things that you have to do as a parent. Like one of the things that you look at in rodents is like pup retrieval. So like you have all this bedding and your like, in your cage and like your little pink pups get lost in the bedding and you have to be able to like smell them and find them. And so a lot of that involves like auditory stimuli and smell, right? Like you have to know the odor of your baby in order to be a sensitive parent, at least within like a rodent framework. So, I mean, a lot of this stuff is like pretty baked into us because it's important for us to survive as a species.

So things like detecting cry, knowing your baby's cry apart from other babies and having a sense of what the baby needs, like all of that is really adaptive so that you can comfort the baby more effectively. And there was like a theory when my kids were babies, I don't know if it was ever like confirmed that like the vowel sound that started a cry could tell you if they were hungry or tired or they needed a diaper change so you could listen to like specific tones in the cry and it would tell you what to do. But I never had any luck doing that with my kids. Like, it just sounded like they were crying. So.

I don't know. I'm sure there's like a program of research out there that someone's either working on or should be working on because it is really interesting to look at like auditory frequencies within cry.

Adam: Yeah. Maybe I'll find someone who's studying that and get them on the show.

Darby: Yeah, I will listen to that episode for sure.

Adam: So I've talked to 50 dads, more than 50 dads and couples on the show. And one of the themes that comes up a lot is this idea that dads can often feel kind of indifferent to their kids when they're born, like they don't have that immediate kind of hormonal, you know, connection because they didn't grow the human and their body didn't do those physiological changes to get ready for raising a kid. That may or may not be related to brain changes, but I'm just kind of curious if, you know, and most dads say, well, like, eventually I got there, but for a while, I just looked at this thing like it was a, what did somebody call it? A potato that eats, sleeps and poops. Which I thought was a hilarious description. You know, do you think that there's connection between that brain change and the, this sort of feeling of maybe indifference is just, is not the right word, but like not immediately connected to the kid in the same way that the mom

Darby: Yeah, my hunch is there probably is a link between how dads are feeling soon after birth and maybe what's happening biologically for them. And I think that's a really common refrain from dads that, you know, they just feel a little, like, left out or they're sort of not part of the, you know, Immediate bond because the mom has such a head start, like assuming it's a biological pregnancy and, you know, obviously adoptive and foster parents are a different situation.

But you know, she's had all this time to get to know the baby and we do give dads in my lab a questionnaire about fetal attachment, like how attached do you feel to the unborn baby? How much are you thinking about the baby? And that did track with the brain changes that we found, suggesting that, you know, as dads are getting prepared to parent, that is mirroring what we're seeing in the brain. But I would also tell parents, both dads and moms, you know, not to get too hung up on the idea that you have to feel that instant connection right after birth. Like, I think the best thing for any parent is just experience and learning. It's like you learn your baby's signals. You learn your baby as a person through interacting with them.

So if dads aren't feeling connected and then their response is to kind of like step away and be less engaged, that's only kind of going to perpetuate that problem and that feeling. Whereas really investing the time to get to know the baby Is probably the best way to form that bond that bond is gonna come online over time.

As you said.

Adam: Yeah. So I wanted to talk about that bond forming process. And I wanted to ask you about parental leave a little bit. So we've made some and I put some in air quotes strides with new moms when it comes to parental leave. Now I'm in a bit of a bubble. In that I live in California and I work at a tech company and we tend to be a little bit more forward thinking and liberal about this stuff.

But, that's not everyone's experience as a new mom. But I think we have an even farther way to go in the U. S. around co parenting and dads and what it means for a dad to take time off when their baby is born. So I wanted to ask you about the future applications of your research here. What are some things that you'd like to see come of this research and specifically around paid family leave or support for new parents and dads specifically? It's not really a thing that we talk about very much for dads.

Darby: Yeah, I'm really glad you asked that because I think that's really one of the reasons that I wanted to write the book that I'm working on, which is about it Dad brain, working title is dad brain. And I think that the research does help to make a case for why we need to invest in early parenthood for both men and women.

We want to protect time to bond and to form a relationship. And I think often because men assume either, I don't have a fundamental instinct in the first few months that makes me well equipped to care for a baby. Or because maybe companies or policymakers don't think it's as essential for dads to be there.

There just isn't as much of the public support for family leave for dads. But I would say like the take home messages of my research are, A, the transition to parenthood is a really dynamic time of transformation across a lot of different domains. And when you see a lot of change, you see vulnerability, you see opportunity.

You want to shore that time up by investing in anything you can do to reduce stress and promote bonding, right? Like you want to set the stage for healthy family relationships going forward because we know that kids do better if they have more involved dads, they fare better economically, they have better academic achievement, they have better occupational attainment, they are going to contribute to the economy more productively, to our national security, they're going to commit fewer crimes, like all of this is worth our taxpayer money.

Right. If we can do things that will improve child welfare long term. And also the health of dads themselves and the health of their partners, right? If you look at things like postpartum mental illness, which we think of as like a mom thing, but you totally see in fathers as well. What can we do to prevent that?

Well, protecting dad's time and ability to sleep in the first few months is really huge. So I think we can build a case like we're such an outlier as a country compared to other advanced democracies or industrialized societies like my brother in law who's Italian got like six months off after his babies were born, right? In Finland, in Sweden, like there's leave that's specifically earmarked for dads, for men. If they don't take it, the couple loses out on the leave. And that's to motivate dads to be more involved. In the U.S., the expectation is often like a week. Maybe two weeks, right? And I worry you mentioned like you're at a pretty progressive place, progressive company.

You don't necessarily want like a tale of two cities where like you have knowledge workers who are getting great benefits and their kids are flourishing and then everyone else is a gig or shift worker who's kind of on the outskirts of the economy. Without any protection and their kids are going to suffer.

So you don't want to create like a huge class divide. I don't think, in this country you know, one of the things that's made our country, I think really successful is that we've had a strong middle class. And so I worry about the polarization of benefits like this that are much more concentrated among the most sought after workers.

Adam: Yeah. Yeah. I couldn't agree more with you on that. So you did mention your book that you're in the process of writing. The working title is dad brain, which I love. It's probably gonna be the working title of this podcast episode. Congratulations on the book also I'm sorry, I've heard that's an incredibly taxing process to write a book.

I've not done that myself. I have no plans to, but excited for this book. So what are your next steps with your book? And what are you excited about in the kind of the future research and exploration that you're going to do?

Darby: Yeah, so I'm honestly super excited to be writing the book. I feel like I have been an academic writing scientific papers for quite a long time. So it's actually like a really fun vacation to get to just like do storytelling. So, I mean, we'll see, the book deal came through just about a month ago, so I'm still in the, like, happy stage where I'm really excited to write. There'll definitely be some kind of crash ahead but I've got my color coded spreadsheet and I'm trying to just bang out lots of words every day and, and it's so fun because I've been talking to dads, as I know you do for your podcast. And just hearing different kinds of stories to kind of like try to put a little more human interest on the research.

And there are just so many cool ways to be a dad. And I think there's so much that's changing in society about the role of fathers that it seems like an interesting time to be writing about this topic. So, that's what's happening on the book. In terms of the research, we are now doing a seven year follow up study in my lab.

So we're bringing the kids and families back that we recruited in pregnancy. The kids are all now six and seven years old, so they're kind of like early school age. And we're seeing how they're doing, what their brains look like with the goal that we can then link that back to what we measured in the dads and in the parents before the baby even arrived.

So I'm really excited about that. It'll take us another couple of years probably to complete that data collection and start to analyze the data. But I have a great team of grad students who really do like most of the work. So they're just gonna chug along and I'll get to work with them on lots of interesting projects that we're planning.

Adam: That's amazing. You're able to kind of do a longitudinal study here over, over time. Will you have the parents and the six and seven year olds back again, maybe when they're teenagers or something like that,

Darby: Yeah, I would love to, I would love to do like a seven year, so like an age 14 maybe. Have you seen that, docuseries Seven Up?

It's like a, oh, it's so good. You should watch it. It's like a British documentary where they recruited seven year olds and they interviewed them and then they checked in with them every seven years.

And I think now they're like, what's a multiple of seven? I think they're like 63 years old. So they've been doing this since the sixties and it's just really interesting to see like which kids were going to have really successful lives, which kids were going to struggle, like in some ways you can tell even from the first set of interviews. But I feel like my lab is kind of trying to do like seven up, right? So we're doing the seven year, we could do like an adolescent one. Maybe we'll follow up with them again in emerging adulthood. We just have to get the grant funding and then our samples also small and it got smaller because of the pandemic.

So that's always the struggle too is just to make sure we have like a viable enough number of people that are willing to come back that we can do the research and have enough statistical power to actually test hypotheses.

Adam:Well I'm very excited for this research and the pending book. Maybe I'll do a startup dad giveaway of some copies of the book or something when it comes out, I'm sure you'll be doing the book tour, which is always very exciting. Based on your universe of findings and you've done a lot of research in this area. What is some of the advice that you would give to new fathers who are navigating the challenges of early parenting? And I suppose this could be broadened to new parents in general, but knowing what you know about dads and having studied that I'll put that spin on it.

Darby: Yea, that's a great question. I mean, I would say hang in there. It gets better. But I mean, I think one thing to note is that because your neurobiology is changing during this time, you're You know, I mentioned this earlier, like change brings vulnerability and opportunity, right? So I think where the vulnerability comes in is for increased stress, more problems sleeping, more mental health problems, be prepared for those things.

I think ways to prevent some of the worst consequences of the stress and challenge is to do as much as you can before the baby arrives to kind of work on communication with your partner, think about who's going to do the baby care you know, what are your values as a family, like all of those hard conversations that, I think are very difficult to have when you're up in the middle of the night trying to comfort a screaming baby, but that you can start to lay some groundwork for productive collaboration in pregnancy.

And then the other piece is to maintain strong social support networks. Parenting can be really isolating. And I think for men in particular, like women are sort of inducted into this secret society of other moms where there's tons of Facebook groups, there's tons of resources, there's community groups, there's meetups. And men don't really get that same, like, infrastructure around, like, bonding with other dads. That's why I think it's great that you do this podcast. I think it's great when dads can talk about being dads. Like, because finding community is such an important part of being a healthy, happy person.

So I would say like invest in friendships, invest in extended friendly relationships, know who you can ask for help, like have people that can come over and hold the baby make sure that if you have things you care about, hobbies or passions, that you're still doing those. And also that you're. Really maintaining good sleep hygiene because that's the piece that can fall apart the most and really challenge the rest of your functioning.

Adam: Thank you for sharing that advice. Really, really good. And some stuff that we haven't heard yet on the show. So I appreciate it. And it's backed by science. So there we go. Final question for you. How can people follow along with your journey and support you or be helpful?

Darby: Oh, that's such a good question. I mean, I would say like, try to buy my book. So it's, I'm writing it now. I'm hoping to turn it in next spring. So probably will be out for Father's Day 2026, which I realize is a really long time. But you know, it'll probably go by quickly. And I'm hoping to do more speaking and more outreach and connection with that.

And I'm not always that great about keeping like Twitter and Instagram and stuff up to date, but people can find me on Twitter. I'm @Darbysaxbe and yeah, I'm just happy that people are interested in this work.

Adam: Awesome. Me too. I am excited to get your book. Many copies of it when it comes out. I'll be waiting even though it's a couple of years in the making, but what a journey. Last question, I guess I, I lied. We do have one more bonus question and then we're going to do rapid fire. It wouldn't be startup dad without that. I understand that you are in a mom's band. Could you tell me more about this wonderful project? Tell me about your mom band.

Darby: Yes, I am excited to tell you about my mom band because we actually just played a show a couple days ago. So, this is a band of moms that formed on the playground of our kids elementary school about eight years ago. So my oldest kid, I think, was in kindergarten or first grade. So really early in elementary And there was this, like, you know, I live in LA, so everyone's a musician.

I'm married to a music producer. There was this awesome dad band that, like, played everything. They, were at all the school events. And some of the women started talking and saying, like, this is setting the wrong example for our daughters. Like, we should be, like, also performing and also doing music.

And I had been playing guitar since high school. I'm a huge music fan and had been like totally dormant and hadn't picked up a guitar in 10 years and similar stories with the other women. One had played bass in a couple bands. One had picked up the drums, but then put it down. One wanted to sing.

We all like picked up our instruments and we started playing together once a week. And we've had ups and downs. The pandemic was an extended hiatus, but in the last couple of years, we just all realized this makes us really happy and started committing more to those weekly practices. And we have a studio space.

We turn the amps up all the way. We have distortion pedals and we learn songs and then we play at our local bar, which is right around the corner, luckily. So I can just carry my amp over and set up. Um, But I think it sort of goes back to the importance of just like having hobbies and outlets, because honestly, like if I didn't have the chance to do the band, I think my life would be much less fun.

Adam: Yeah. Sounds like it sounds like an awesome thing. Well, is there a particular genre that you focus on?

Darby: Yeah, it's kind of like indie rock, like almost like, like 90s, 80s, like a lot of new wave, like we play like Breeders songs.It's mostly covers. We have a couple original songs, most of which are about our school and our neighborhood. But let's see, what did we play on Sunday? We played a Killer song. We played a song by this band Throwing Muses. So just like deep in the vault stuff that we like to play.

Adam: And does the band have a name?

Darby: Well, so our kids went to Dahlia Heights elementary school, which is our local neighborhood elementary. So we are called the Dolly Mamas.

Adam: I love that. What a great what a great thing to end on the Dolly Mamas. Love it. Thank you for sharing that. Are you ready for some rapid fire?

Darby: I don't know, but I guess we'll find out.

Adam: No one's ever ready for rapid fire, but there's one rule and that is I ask you a question and you say the first thing that comes to mind and then we move on and it's a judgment free zone but full of laughs.

So here we go. What is the most indispensable parenting product you have ever purchased?

Darby: Diapers?

Adam: What is the most useless parenting product you've ever purchased?

Darby: Oh, the nasal irrigator thing that you suck out.

Adam: Okay, finish this sentence. The ideal day with my kids involves this one activity.

Darby: Hiking somewhere beautiful outside without them complaining.

Adam: What is the best piece of parenting advice that you've ever received?

Darby: It's okay to ignore your kids sometimes.

Adam: What is the most frustrating thing that has ever happened to you as a mom?

Darby: I mean, my kids general bad attitudes?

Adam: All right, now, as payback, what is the most embarrassing thing that you've ever done in front of your kids?

Darby: Oh, they're there. The list is way too long to go into. I'm constantly doing embarrassing things. I don't know. When my daughter was a toddler, I like somehow managed to knock all the shopping carts at Trader Joe's, like across the entire parking lot. And she was just starting to talk. And for a while, all she would say to anybody was mommy knocked the carts.

Like they banged into everyone's cars. They were like going everywhere. So that was really embarrassing.

Adam: That’s amazing. I blame a brain volume loss or mass loss for sure. Have you ever secretly thrown away a piece of your kid's artwork?

Darby: Constantly

Adam: What is the most absurd thing that one of your kids has ever asked you to buy for them?

Darby: A dog, but then we did it.

Adam: Congratulations! Also a dog parent now. What is the most difficult kids TV show that you've ever had to sit through?

Darby: Oh, wow. I think in… what's it called? Inspector why, or what's the one where it's like, they're asking why.

Adam: Yes,

Darby: Do you know what I'm talking about?

Adam: know what you're talking about. I cannot remember the name of it off the top of my head, but we'll find it and link to it in the show notes.

Darby: Yeah, that show drives me nuts.

Adam: What is your favorite kids movie?

Darby: Oh I mean, it's, this is a very obvious psychologist answer, but probably Inside Out.

Adam: And the sequel is about to come out. Very excited.

Darby: I’m excited for that.

Adam: Love that movie. I've heard it's actually very kind of accurate to some of the stuff that happens in the brain. Is that true?

Darby: they consulted with real researchers when they were developing it, and I have a postdoc in my lab who's really, really interested in mixed feelings and sort of ambivalent emotions and I think the new movie's all about that. So he's very, very excited.

Adam: Awesome. What is the worst experience that you've ever had assembling a children's toy or a piece of furniture?

Darby: I mean, Ikea is not your friend, but I have a husband who's very handy, so usually I give him the box and watch him swear for a few hours.

Adam: Awesome. How long can a piece of food sit on your floor and you will still eat it?

Darby: Probably years, honestly. I mean, if it's something dried, but I would say like maybe a couple weeks.

I have a friend who studies moral foundations of emotion, and it turns out that your disgust threshold is really correlated with political attitudes. So, like, I'm pretty liberal, but I also have a very low disgust threshold, which tracks.

So, yeah, I'm like the person at a coffee shop that if like someone's leaving their piece of cake, I'll be like, you know,

Adam: That's amazing.

Darby: Just give me a fork. Yeah. Probably not something to brag about on a public podcast.

Adam: That's okay. What nostalgic movie can you just not wait to force your kids to watch with you?

Darby: Oh, I've forced my kids to watch most movies now that they're teens, but I'm really glad my daughter loves the movie Rushmore, which is like one of my favorites. And my other favorite movie is the Beatles movie, A Hard Day's Night. And my kids don't really love it, but I do force them to watch.

Adam: Awesome. How often do you tell your kids back in my day stories?

Darby: At least three times a day.

Adam: And finally, what is your take on minivans?

Darby: Anti. I'm all about the compact car. I actually think that it's like, we have such an indulgent culture that we need so much personal space. Like, I'm all about kids sharing tiny bedrooms and being cramped into little cars like I was as a kid. I think it builds character.

Adam: I was going to say character, resiliency, grit, all the things. That's a great question to end on. Thank you, Darby, for joining me on Startup Dad has been fascinating. I learned a ton and I'm so appreciative of you taking the time.

Darby: Totally my pleasure. Really fun to talk to you.

Adam: Thank you for listening to today's conversation with Darby Saxbe. If you enjoyed the show, please subscribe, share, and leave me a review on Apple or Spotify. It'll help other people find this podcast. Startup Dad is a Fishman AF production with editing support from Tommy Herron. You can join a community of over 10,000 subscribers and stay up to date on my thoughts on growth, product, and parenting by subscribing to the Fishman AF newsletter at www.fishmanafnewsletter.com. Thanks for listening, and see you next week.