How to nurture the flourishing of your baby's or toddler's brain

This article is part of a collection inside The Possums Sleep Program called Deeper Dive, which explores the complex scientific, historical and social contexts in which families and their babies or toddlers live and sleep. You don't need to read Deeper Dive articles to be helped by The Possums Sleep Program.

Why do our babies and toddlers have such a fierce hunger for rich and changing stimulation?

At birth, Homo sapiens are remarkably neurologically immature compared to other primates. The newborn human is not entirely helpless though, because she is able to communicate whether or not her biological needs are being met through bodily movements, facial expressions and making sounds (which is also a form of movement), and the way her sympathetic nervous system dials up or down.

Evolutionary biologists hypothesise that the human baby is born so incredibly dependent upon adult care because the mother's body is unable to cope with the metabolic load of sustaining the foetus's life beyond nine months gestation. This explains why

• Our newborns have dramatically fewer hardwired neural pathways, and fewer pre-existing behavioural patterns in response to the environment at birth, than any other primate newborn.

• For the whole of the first three years of life, our little ones are exceptionally neuroplastic. That is, our babies and toddlers experience an unusually vivid, intense, and prolonged neural and synaptic blossoming in response to the environment, relative to all other creatures on this Earth.

This exquisitely plastic little brain, which is also very big in size compared to other primate newborns, is learning at an astonishing speed from birth, day and night. From birth through to the end of toddlerhood, one million new synapses are connecting up every second in her brain. This extroardinary explosion of neural connectivity occurs in direct response to environmental and social stimulation. This explains why

• Human babies and toddlers are astonishingly mentally, socially and emotionally sensitive and flexible

• The human infant is exquisitely adaptive to the particular culture, geographical region, and micro-environment into which she is born

• The human brain is more capable than any other species of acquiring highly complex social and technical skills.

From two years of age, alongside this wild and flagrant blossoming of neuronal synapses, a remarkable neural refinement by pruning also ramps up. The plasticity of behaviour which results from our Great Synaptic Flourishing in early life is fundamental to the brilliant social intelligence of our species, and has given Homo sapiens our evolutionary edge.

It also explains why our babies and toddlers are voraciously hungry for rich and complex environmental sensory motor and social experiences, and dial up if they are not receiving enough stimulation to satisfy this hunger.

What might get in the way of your baby or toddler's Great Synaptic Blossoming?

The accurate answer to this question is "poverty, trauma, disease, injury, and physical or emotional abandonment". This accurate answer would elaborate on the importance of nutrition, shelter, warmth, nurturing love, and protection from disease, injury and abuse. These are human rights not afforded to many babies and toddlers around the world, mostly for reasons outside their families' control. But in my discussion here, I will assume that the fundamental needs and human rights of the child are met.

Human babies and toddlers are remarkably adaptive across a great diversity of infant care practices. And around the planet, babies and toddlers thrive in the care of their families even in the midst of terrible adversities.

But each family wants the best possible future for their small child, and each family has the right to a life with their little one that is as enjoyable and satisfying as possible.

Our babies and toddlers learn best when they are dialled down, that is, when they are not exposed to persistent sympathetic nervous system and hypothalamic pituitary adrenal axis hyperarousal.

Stress is a necessary and normal part of human experience, but high levels of sympathetic nervous system arousal, prolonged over time, interfere with learning and wellbeing, and have long-term effects.

The Possums programs, and The Possums Sleep Program, aim to help you and your little one get in sync, and to promote resilience and wellbeing for you, your little one, and your family, now and into the future, by

• Helping you keep your little one as sensibly dialled down as possible

• Giving you ideas for your little one's rich and changing sensory motor adventures

• Helping you enjoy the days and the nights with your little one just as much as you can.

Our health systems have not yet properly grasped the implications of the extraordinary neural flourishing of babyhood and toddlerhood

I have the view that in the West, our health systems have not yet fully grasped the clinical implications of the Great Synaptic Blossoming of the baby's or small child's brain.

For instance, we haven't understood how voraciously the global neuronal workspace of the human infant craves rich and changing sensory motor experience, whether newborn, baby or toddler, and what the effects of not providing enough might be, including on cry-fuss behaviours, sleep, sensory motor development, and long-term sensory dysregulations.

Paradoxically, from the early 1900s, advice to avoid overstimulation has been a dominant health system response to fussy babies or babies and toddlers with sleep problems. You can find out more about this for babies here and toddlers here.

Why do the first 100 days of life matter so much?

In particular, I have the view that health systems in advanced economies fail to grasp the importance of supporting neurohormonal synchrony between a mother and baby, parents and baby, in the first 100 days of life.

The first 100 days are a critically important window of time in which to protect developmental trajectories. I have proposed elsewhere that the biomarkers of the exquisite neuroplasticity of the first three months of life are

• Persistence of the cortical subplate

• Persistence of baby's writhing general movements

• Peak levels of monoaminergic activity.

These biomarkers correlate with the behavioural marker of the tendency to cry a lot and get caught in crying loops in the first 100 days of life.

The steps we can take to best protect the incredible neurologically sensitive infant brain in this window of time are discussed in The discontented little baby book, in the collection of articles called When baby cries a lot: brief & simple summary, starting here, in Possums Breastfeeding & Lactation, and in The Possums Sleep Program.

What do babies and toddlers need to flourish?

Your baby or toddler will flourish in response to

1. Your responses to her, and her capacity to elicit responses from you, and from other loving people in the world around her, to and fro, back and forth. Sometimes she initiates and you respond, other times you initiate and she responds. Both are vital. You can find out about this for babies here and here, and for toddlers here.

2. Facilitating her great and biologically driven curiosity to explore the world. I call this her hunger for sensory motor nourishment. It's as powerful as her thirst and her hunger for food, just not as immediately life threatening if unsatiated. You can find out about this for babies here and for toddlers here. Sensory motor enrichment (which includes social communication) is foundational, resulting in the flourishing of her global neuronal workspace.

3. Play, a kind of sensory motor engagement with the world which allows her to experiment and develop a rich imaginal life. In babies, this might be looking for wrapt attention or the smile or laugh in enjoyable physical and sound-based interactions. In toddlers, this means following her imaginative lead, entering into her little world at times.

4. Social and emotional development and motor development interact together. In the West, we often forget about the physicality of interaction with our small child, since we are more verbally and less physically focussed than many cultures of the global majority are in interactions with infants. Your little one needs the

   • Physicality of interaction with, or play with, older children and adults

   • Physicality of your or someone's response when he is dialling up. That is, your nurturing and physical response to the physicality of her emotions (not just verbal responses)

   • Physicality of interactions with objects in his world. Toys and objects inside the home really aren't the critical ingredients for brain development. It's outdoor play or play with other children, and physical interaction with objects or features in the environment which can be imaginatively transformed during play, which matters.

5. Avoidance of an overdose of the aspects of our society which can interfere in development of social or motor skills, such as screen time, or time spent in environments that aren't suitable for toddlers to explore.

• You can find out how to protect toddler motor development here.

• You can find out about protecting your toddler's social development here.

• You can find out about Tuning into Toddlers Online here.

Your small child is a precious citizen of our planet's future. What unknowns await her? What skill, sensitivity, courage and resilience will your child require, as this most extraordinary century unfolds?

Perhaps, as I did once, your heart aches sometimes as you watch your little one. We have such big dreams for our baby or toddler, and so many fears! Before all else I wanted to take care of my beloved small child, so that she thrived, so that he was happy enough of the time in his life, so that she found nurturing relationships, so that he was ready to play his part bravely in the great and perilous human project.

I hope my work brings you encouragement and helps you find joy with your small child through these early days of your parenting odyssey.

Recommended resources

Center on the Developing Child, Harvard University, found here.

I recommend Tuning into Toddlers Online (TOTOL), by Professor Sophie Havighurst and her team at Mindful, The University of Melbourne, Australia, if you're interested in learning more about shaping your toddler's behaviours in a way that keeps emotional connection strong. You can find out more here.

Selected references

Douglas PS. Pre-emptive intervention for Autism Spectrum Disorder: theoretical foundations and clinical translation. Frontiers in Integrative Neuroscience. 2019;13(66):doi.org/10.3389/fnint.2019.00066.

Dunsworth HM, Warrener AG, Deacon T, Ellison PT, Pontzer H. Metabolic hypothesis for human altriciality. Proceedings of the National Academy of Science in the USA. 2011;109:15212–15216, doi: 15210.11073/pnas.1205282109.

Fogel A, Greenslapn S, King BJ, Lickliter R, Reygadas P, Shanker SG, et al. A dynamic systems approach to the life sciences. In: Fogel A, King BJ, Shanker SG, editors. Human Development in the twenty-first century: visionary ideas from systems scientists. Cambridge: Cambridge University Press; 2011. p. 235-253.

Gottman JM, Katz IF, Hooven C. Parental meta-emotion philosophy and the emotional life of families: theoretical models and preliminary data. Journal of Family Psychology. 1996;10:243-268.

Havighurst SS, Kehoe CE, Harley AE. Tuning in to Toddlers: Research protocol and recruitment for evaluation of an emotion socialization program for parents of toddlers. Frontiers in Psychology. 2019;10(1054):doi: 10.3389/fpsyg.2019.01054.

Havighurst SS, Kehoe CE, Harley AE, Thomas R. A randomized controlled trial of an emotion socialization parenting program and its impact on parenting, children’s behavior and parent and child stress cortisol: Tuning in to Toddlers. Behavior Research and Therapy. 2022;149:104016.

Johnson AM, Hawes DJ, Eisenberg N. Emotion socialization and child conduct problems: a comprehensive review and meta-analysis. Clinical Psychology Review. 2017;54:65-80.

Matricciani LA, Olds TS, Blunden SL, Rigney G, Williams MT. Never enough sleep: a brief history of sleep recommendations for children. Pediatrics. 2012;129:548.

Rosenberg KR. The evolution of human infancy: why it helps to be helpless. Annual Review of Anthropology. 2021;50:423-440.