Daddy brain: how parenthood changes menDaddy brain: how parenthood changes men
All In The Mind
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, PhD Clinical psychologist Professor of Psychology, University of Southern California Author, Dad Brain Credits: Presenter/producer: Sana Qadar Senior producer: James Bullen Producer: Rose Kerr Sound engineer: Roi Huberman To 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.
29:35•6 Nov 2026
Shrinkage, Testicles and Dad Life: How Fatherhood Rewires Men
Episode Overview
- Men’s brains show structural changes after a baby arrives, especially in regions that support understanding a child’s mind.
- The extent of brain change in fathers is linked to how much hands-on childcare they do.
- Normal drops in testosterone in involved dads are adaptive and support nurturing roles rather than signalling poor health.
- Couples often misjudge how baby care will be divided; dads who do more tend to feel less stressed and more satisfied.
- Parenthood can reduce day-to-day fun but increase long-term meaning and purpose, which supports wellbeing over the lifespan.
“Parenthood is a little low on hedonic well-being, but it can be really high on eudaimonic well-being.”
In this eye-opening episode, you'll learn about how becoming a dad can literally reshape a man's brain, body and daily life. All In The Mind turns its attention to fathers, with clinical psychologist and USC professor Darby Saxbe sharing years of research and her own family story. You’ll hear how her "pretty typical 1980s American dad" became a calm, routine-loving solo parent after divorce, and why that experience pushed Darby to study fatherhood scientifically.
She explains that men’s brains can shrink by about one per cent after a baby arrives, especially in areas that help them understand other people’s thoughts and intentions. As she puts it, these changes reflect "remodelling to enable greater efficiency" in reading a baby who can’t talk yet. The episode leans into the surprising stuff too: testicular scans, testosterone drops and evolutionary theories about "quantity" versus "quality" reproductive strategies.
Saxbe describes research where bigger testicles were linked to less focus on caregiving, and breaks down why lower testosterone in hands-on dads is actually an adaptive shift, not something to panic about. Relationship tension and division of labour get frank attention. Darby’s studies show couples often overestimate how much dads will do, and that men who end up taking on more baby care report lower parenting stress and better relationship satisfaction.
She distinguishes between short-term fun and long-term meaning, noting that "parenthood is a little low on hedonic well-being, but it can be really high on eudaimonic well-being". For dads wondering what truly matters, Saxbe’s advice is simple: get stuck in. The more nappy changes, night feeds and play sessions, the more the "parenting brain" comes online and the more rewarding fatherhood becomes.
If you’ve ever wondered how fatherhood can hurt your sleep but help your soul, this one might have you looking at dad life in a whole new way.
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