In an interview with Ignacio Pereyra, guest editor of Early Childhood Matters and journalist, Dr Shir Atzil, a leading researcher in the neuroscience of social connection, explains how our brains develop through relationships, why learning is so central to caregiving, and the importance of caregivers looking after their own “body budget”.
Your research demonstrates that caregivers shape babies’ social brains. Could you explain the idea of the “social brain” in this context?
Some animals are born with a mature brain. They know the strategies to survive – what to eat, how to be safe from predators. The brains of social animals, specifically mammals, are immature at birth. Their brain develops within a social context, shaped by the caregiving system that supports them – that’s their evolutionary survival strategy.
But when people talk about the “social brain”, they’re often thinking only about social behaviours and interacting with others.[1][2][3] What we discovered is that the social brain is not only about socialising. The entire brain is a social brain.[4] Fundamental functions of the brain that are completely unrelated to socialising also develop in a social context, such as regulating our heart rate and our temperature and when we need to eat.
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Atzil, S., Satpute, A.B., Zhang, J., Parrish, M.H., Shablack, H., MacCormack, J.K. et al. (2023) The impact of sociality and affective valence on brain activation: A meta-analysis. NeuroImage 268:119879. DOI: https://doi.org/10.1016/j.neuroimage.2023.119879
From the very beginning, the caregiver provides the physiological conditions in which the infant’s systems mature. As a result, the parent’s wellbeing is, quite literally, the regulatory environment in which the infant grows and develops.
It sounds like you’re talking about homeostasis, which is an idea most people will know – the process of keeping things like our body temperature in a desired range.
I want to introduce the term “allostasis”, which is different from homeostasis. As you say, homeostasis is a process of monitoring and correcting deviations from a baseline – you notice that you’re getting too hot, so you take some action to cool off. Every living system regulates homeostasis, even plants. But animals with a brain don’t have to wait for deviation from a baseline, they can predict and pre-empt it. Homeostasis is feeling hungry and then eating; allostasis is anticipating that I’ll get hungry and packing a sandwich.
Allostasis is really the brain’s most fundamental job: to keep our bodies regulated so we can survive and thrive.[5] A huge network of brain regions is constantly at work, tracking and adjusting our basic physiological processes, things like energy use, eating, immune function, temperature, heart rate, arousal and sleep.
Theriault, J.E., Katsumi, Y., Reimann, H.M., Zhang, J., Deming, P., Dickerson, B.C. et al. (2025) It’s not the thought that counts: Allostasis at the core of brain function. Neuron. DOI: https://doi.org/10.1016/j.neuron.2025.09.028
What this system does is essentially balance the body’s budget, it anticipates what resources will be needed and allocates them efficiently, before the demand even arrives. So instead of waiting to be hungry, cold or stressed, the brain predicts those needs and prepares in advance, constantly adjusting to keep us ready, efficient, and stable enough to act in the world.
Your research shows that allostasis is a social process, to a surprising extent.
For social animals, like us, the body operates not through individual physiology, but through social physiology – our physiology is more efficient when we are together. We have data showing that when we eat together, it’s less effortful for our body to digest the food. It’s less effortful for our body to keep warm when we’re with others than when we’re isolated. Social relationships mean we spend less energy on meeting our basic allostatic demands. We’ve shown that when people have partners, they are better at regulating their glucose levels, which is a major contributor to obesity and diabetes.
Regulating our allostasis is something our brains have to learn how to do, and we learn it socially through interaction with a caregiver. Babies are completely helpless in regulating their own allostasis. They’re completely dependent on the caregiver. If they’re hungry or hot, they signal it to the caregiver by crying or showing discomfort. If there’s a caregiver around, the caregiver hopefully addresses the cause of the discomfort, by providing food or cooling them down.
So when a caregiver is responsive, the infant learns better how to regulate their own allostasis – and that can lead to health benefits later in life?
Not only that. Over time, as the caregiver regulates every aspect of the infant’s needs – warmth, food, comfort, sleep – the infant brain learns that the caregiver is the key to survival. You learn that your life depends on another human. This is how we learn to love people who positively impact our allostasis. This understanding overturns a long-standing assumption: bonding is learned, not pre-programmed. The infant–caregiver bond sets the foundation for developing bonds and love in all other relationships.
The term “synchrony” is a bit of a buzzword, but I guess it’s important here. What does “synchrony” mean in the context of a parent–infant relationship, and why does it matter?
Synchrony is correlated with good stuff, from the early years to adult life, but it’s not magical. Think of a caregiver regulating an infant’s temperature through skin-to-skin contact, or, through breastfeeding, sharing antibodies that strengthen the infant’s immune system, or using touch and tone of voice to synchronise attention when teaching something: “this is an apple”. A synchronised parent–infant dyad is usually predictive of better emotional development, better cognitive development, better health.[6][7][8][9] So, we can reframe the concept of “synchrony” from something magical that just happened to a very useful strategy that is being used for social physiology, for social allostasis.[10]
Feldman, R. and Eidelman, A.I. (2004) Parent–infant synchrony and the social-emotional development of triplets. Developmental Psychology 40(6): 1133–47. DOI: https://doi.org/10.1037/0012-1649.40.6.1133
Feldman, R. (2007a) Parent–infant synchrony and the construction of shared timing; Physiological precursors, developmental outcomes, and risk conditions. The Journal of Child Psychology and Psychiatry 48(3–4): 329–54. DOI: https://doi.org/10.1111/j.1469-7610.2006.01701.x
Feldman, R. (2007b) Mother–infant synchrony and the development of moral orientation in childhood and adolescence: Direct and indirect mechanisms of developmental continuity. American Journal of Orthopsychiatry 77(4): 582–97. DOI: https://psycnet.apa.org/doiLanding?doi=10.1037%2F0002-9432.77.4.582
Feldman, R. (2007c) Parent–infant synchrony: Biological foundations and developmental outcomes. Current Directions in Psychological Science 16(6): 340–45. DOI: https://doi.org/10.1111/j.1467-8721.2007.00532.x
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We’ve talked about what’s going on in the infant’s brain. What’s happening with the caregiver?
As caregivers, we actually learn to incorporate another human being into our own regulatory system. So when we care for someone else, the brain begins to make those predictions not only for ourselves, but also for our infant. When our infant is in need, the same system responds as when we ourselves are in need; when their needs are met, it’s almost as rewarding as meeting our own. Anyone who’s been a parent knows: if your infant is screaming with hunger, it’s more urgent to feed them than yourself.
People talk about parental intuition, but it’s about learning, not intuition. I feel when my infant is hungry because I learn their rhythms and needs from spending a lot of time together. So “parental intuition” is really very efficient learning from a hyper-intentional focus on the infant’s needs. I don’t want to wait for my infant to scream before I feed them; I want to anticipate and provide what’s needed early, which requires significant effort. It’s hard. The caregiver’s brain is now performing allostasis for their infant as well.
Does this explain why parents need support from others?
It’s a really good question. To be able to take care of another human, you must have sufficient resources. Especially for mothers who are exhausted from birth, the caregiver’s body budget is critical. The parent’s wellbeing is the regulatory environment for the infant. The parent’s emotional state is the biological environment where infants develop. If you’re completely depleted, you can’t provide for someone else efficiently, especially not intentionally. If you have some emotional or psychological hardship, your own allostasis suffers, and you’re less efficient at regulating your infant – you have less energy to sense and address the infant’s cues. That’s where synchrony can suffer.
Sometimes interacting with your child strengthens you, but sometimes you need space, adult time, meeting a friend, professional development, a hobby. The concepts of allostasis and body budget help us approach this non-judgementally. It’s not about being a good or bad parent, but about having sufficient resources to be a caregiver. Taking care of yourself as a caregiver isn’t just for your own sake, it’s what’s best for your child, like putting on your own oxygen mask first. If your own resources are running low, you need to find ways to top them up – daycare, babysitter, partner, family members.
So we should reinforce that allostatic needs can be met by other adults, not only biological parents.
Yes, this is important. What infants need to optimally develop is a fine-tuned regulation of their allostasis. As long as the infant’s allostasis is taken care of, the infant is good. Any adult who is invested in the infant is good enough, as long as the infant learns this is a person they can rely on. This helps us be less judgemental about who’s taking care of the infant. It doesn’t matter if it’s mummy and daddy, or two daddies, or a single mum getting help where she can. It doesn’t matter if you’re a birth mother or an adoptive mother. What matters is that the infant’s allostatic needs are being consistently met in the context of an attentive other.
What would you say to parents who are struggling?
First, acknowledge your hardship. Realise you’re caring for two people’s allostasis. It’s like an intensive care unit: high responsibility around the clock, a lot of effort, but it’s transitional, as infants’ brains gradually mature, taking over much of the responsibility for their own allostasis. Also, focus less on judging how you behave as a parent and more on the infant’s allostatic needs. Let others feed or comfort your child; it doesn’t have to always be you. Self-care isn’t selfish – it’s the best thing for both of you.
Since allostasis is such a central process to our brains, a depleted body budget is experienced as emotional distress, which can be improved by sleep, food, movement and exercise. After sleepless nights, things look grim, but rest can reset perspective. Focus on the biological reality of caregiving – it helps clarify strategies and reduce guilt.
And what would you most like policymakers to understand about your research?
We need to change the way we think about wellbeing, it’s not something individual. Humans are not built to function in isolation. Our bodies and minds are interdependent; we are designed to exist together. Supporting caregivers’ physical and emotional health is therefore an investment in children’s development. When parents are well-regulated, resourced, and emotionally supported, they can attune to their children and create the synchrony that allows development to flourish. Caring for parents means caring for children, and caring for society.
Funded by the European Union. Project 101116444 — BIOBOND
