by Anna Machin
One other aspect of your life history, influenced again by the unique way your species apportions its lifetime’s quota of energy, is the number of developmental stages you pass through, when these occur in your lifespan and how long they last. As a general rule, the ‘live fast, die young’ gang tend to whip through the earlier stages to arrive at adulthood, and the opportunity to reproduce, as quickly as possible. Conversely, as we know from Chapter One, those of us with large brains need to take our time reaching maturity and spend many years in the early stages.
In terms of the actual stages, the vast majority of mammals, including our fellow primates, have three: infant, juvenile and adult. They go from milk-dependent ball of fluff, to large and annoyingly energetic juvenile, to fully fledged adult. However, as is so often the case with humans, we have stepped away from this conventional pattern. Instead, we have five life history stages: infant, child, juvenile, adolescent, adult. This makes us a member of – possibly the only member of – a unique group. It is thought that only the whales and dolphins may be eligible to join us. The thing that we species all have in common is our unusually large brains, and the fact that our offspring therefore need extra time before maturity for their brains to grow and to learn to use those brains in the best way to ensure success.
Childhood is a time of exploration – of making friendships, surmounting challenges, venturing into the outside world and hopefully discovering a love of knowledge. However, within the life history world, it is less poetically defined as the time between weaning and dietary independence. Toddlers are weaned early and then need an adult to help them feed themselves solid food, as those of us who have spent many a happy hour with a stack of apples and a food blender know. This is the childhood stage. Initially, these helper adults were female relatives, but from 500,000 years ago onwards, as we learnt in Chapter One, that adult was dad.
The other unique stage is adolescence. Today, a time of deeply felt emotions, sexual, social and creative exploration and wardrobe mistakes. And for dads, like Joseph, a time to ask profound questions about how you can most effectively support your child through this challenging period, so they emerge as an autonomous adult.
I have a good relationship with my father, so it is almost an implicit criticism, but it’s the ways I wish my dad would have challenged me on some of my thinking as a teenager perhaps, and didn’t, probably for good reasons. I would hope to develop and foster a relationship – as they enter teenage life and start to develop their own identities, I think there is an increased question of how you navigate these questions, challenges, opportunities in life – [and] I would hope to develop a close enough relationship with them so we can have these conversations while they are still trying to work it out.
John, dad to Joseph (four) and Leo (two)
More formally, adolescence is the period defined as the time between the cessation of skeletal growth and the onset of sexual maturity. There are numerous debates as to why this stage evolved, but most likely it is to allow our massive brain to finish developing and for vital life-critical knowledge to be gathered without the distraction of an overwhelming urge to find a mate. And studies of teenage brains show us that this is indeed a time of astonishing brain development. In particular, the prefrontal cortex – the site of rational thought – is still under construction, meaning that teenagers tend to respond impulsively or emotionally to situations – driven by their amygdala – rather than taking the time to consider the most sensible course of action. Sound familiar? And when mothers were still tied to the never-ending cycle of pregnancy and breastfeeding, this is the st age when the father’s role became critical, reining in the most excessive and questionable behaviours and acting as teacher and guide. Research shows that fathers are as vital to the development of their adolescents as they are to their toddlers and pre-teens; their role and behaviour subtly shift as their child ages.
But let’s press pause and rewind from the adolescence stage for a moment – we will return there later in the chapter – to the very early years of a child’s life. We know from previous chapters that a secure attachment between father and child is vital for healthy development, and that this attachment is particularly crucial during the first 1,000 days of the child’s life, as it coincides with a time of rapid brain development. In 2015, a group of Dutch scientists, led by Rianne Kok from Leiden University, carried out a prospective study of 191 children to explore the influence that their parents’ caretaking behaviour had on their brain development. A prospective study means that they followed the children’s development in real time, beginning the study when their subjects were just six weeks old, rather than trying to find a link by looking backwards (a retrospective study). Their first step was to gather their gaggle of very tiny babies and carry out ultrasounds of their brains and measurements of their head circumferences to get their starting point, their baseline. They then left the families largely alone for eight years, returning only at age one to measure parental sensitivity during a play session and at ages three and four to observe a parent and child problem-solving play session. After four intervening years they then visited again, when the children were eight, and scanned their brains using an MRI scanner. This allowed them to get the fine detail of brain structure, including how much grey and white matter there was. Remember, the grey matter is the neurones and the white matter the axon fibres that link neurones together, allowing different areas of the brain to communicate with each other. The theory is that the larger the amount of grey matter and the higher the density of white matter, the more ‘advanced’ the brain will be, because it has more neurones and those neurones are better able to communicate with each other as they have more connections. This neural intricacy allows us to display the cognitive flexibility and complexity that defines us as a species.
What they found was that those children whose parents were more sensitive during play and joint problem-solving activities did have larger total brain volume as a result of larger volumes of white and grey matter. As a parallel exists between oxytocin levels in securely attached parents and children, so a parallel existed between the behavioural input that the baby received from their mum or dad and the very structure of the child’s brain. The evidence for the powerful effect a parent’s behaviour can have upon their child’s development was there before them in black (or grey) and white. I think this is amazing. The sensitive parents in this study were actually giving their children the structural foundations for life and endowing them with the neural architecture to enable them to thrive.
Becoming a toddler is a time of fast and furious change in a child’s life. Gone are the days of complete dependency on mum and dad – you are starting to branch out into the world as an independent being. Your language skills are developing but doing so frustratingly slowly, so your words don’t match your needs; behaviours that were once seen as cute in a baby are seen as less so in a large toddler, so you are starting to be reined in by the adults who surround you; and starting pre-school or nursery means you have to learn and adhere to endless rules about the social niceties. No wonder you have the odd tantrum. Throughout this time, a key area of your neocortex – the outer area of the brain where your higher order brain processes sit – is rapidly developing. This area, the prefrontal cortex, is where our executive functions lie. This term refers to a set of skills that allow us to respond flexibly to situations that we encounter. So, here sits our ability to problem-solve, our ability to pay attention and our ability to inhibit our less than helpful behavioural instincts. It’s the bit that goes slightly haywire when you are a teenager. Executive functions allow us to meet new challenges, solve new problems and resist temptations, and in the long run those who possess a fully functioning prefrontal cortex have better mental health, can more effectively regulate their behaviour and do better at school. If children get the most sensitive and supportive input during this time then this area of the brain, and the behaviours it supports, provides a strong foundation as the child navigates life. Ma
ny fathers, like John, give this aspect of the role much thought:
I suppose the ongoing challenge for us is: how do we equip these children to grow up with increasing independence? How do we steer, direct them with the aim of increasing their independence? Certainly, the going to school was for us a stark realization that this is [Joseph’s] next step towards independence from us.
John, dad to Joseph (four) and Leo (two)
And with their focus on rough and tumble play, fathers have a unique role in supporting the development of executive function in their children. We know from Chapter Seven that play is a key component in building the attachment between father and child, particularly in Western families. But the characteristics of this play – the need to pay attention to your co-player’s quick moves, the need to respond in a split second to changes in direction, the need to handle your powerful emotional reactions and the need to confront and surmount physical and mental challenges – make it equally as important in the development of executive function. And we now have solid evidence that involving the child in play during the toddler and pre-school years is particularly important for the development of this suite of skills.
In 2015, a team of researchers from the University of North Carolina and New York University came together to study the impact of parental play on the development of executive function in 620 children from low-income, rural families in Pennsylvania and North Carolina. Children were observed with their parents, mum and dad separately, at the age of seven months and again at twenty-four months. During these observations, parents were tasked with playing with their children. At seven months, this was a free play session but at twenty-four months it was focused on jigsaw puzzles that were of increasing levels of difficulty, requiring mum or dad to step in and help. Parental sensitivity was measured with a sensitive parent being characterized as one who was engaged, warm, responsive to the child’s cues, showed appropriate levels of excitement and supported the child’s learning through play. An insensitive parent was one who appeared to be disengaged, was unaware or responded inappropriately to the child’s needs, made no attempt to teach the child and remained impassive.
One year after the last play session, the researchers returned to the children and carried out tests to assess the executive function of the now 3-year-olds. The tests, made child-friendly with flip books, pictures, shapes and colours, assessed abilities in memory, attention and inhibitory control – the full triumvirate of executive function skills. The results showed that dads’ influence on executive function was most evident at the 24-month play session. Children whose dads supported their play and scaffolded their learning during the puzzle task had better working memory – which is fundamental to problem-solving – attention and inhibitory control. All skills that are essential to the ability to succeed at school and navigate the social world. However, at the age of seven months, dads did not have a separate influence on executive function beyond that of mum – both parents had an equal role to play. It would appear that it is only once the child begins to explore their world and develop a life away from their parents – that is, as they become that uniquely human thing, a toddler – that dad’s unique contribution to development kicks in. And again, his area of key focus is supporting his child as he or she develops the abilities – in this case the cognitive abilities – that will enable them to succeed in the world outside the front door – even if the first step is only into pre-school.
Dan: I feel I am more in this for the long run. I think as they get older they will be a bit more into me. I am biding my time. I am a lot about the giving of advice. I say to them, ‘I am giving this advice to you now, it won’t mean much to you, but some day you will be like, “Ahh!’ ” So, I do feel like [I should] stick with it, not that they are going anywhere, not that I am going anywhere, but I do feel like I will get more out of it when they are slightly older.
Simon: And I love the now. I keep thinking, You’re not going to be cuddly for ever, there is going to be a time when they are like, ‘I don’t really want two dads. I don’t want to be cuddling you, and stop kissing me all over the face with your horrible beard.’
Dan and Simon, dads to Daisy (six) and Bill (five)
In fact, this unique and powerful contribution from fathers to their child’s development extends far beyond the development of executive function. In their UK-based study, a team from Oxford University led by L. E. Malmberg explored the impact of sensitive parenting on general cognitive abilities and language development in ninety-seven families. They were interested in exploring two key questions. Firstly, they wanted to understand whether the sensitive parenting of one parent could buffer the negative impact on development of the less than sensitive parenting of the other parent. Secondly, they wanted to understand whether the links between sensitive parenting and brain development were universal, regardless of your background, or were influenced by a range of socioeconomic factors, such as parents’ education, socio-economic class and family income.
What they found was that the extent to which parents displayed sensitivity towards their children when they were eleven months old had an impact on mental skills at eighteen months and language development at thirty-six months, but this was only the case for mothers if you removed their socioeconomic status from the mix – that is, if you pretended they all had the same background. If you put this in – that is, make your study a more realistic representation of the diversity of the human population – then maternal sensitivity had no impact on these aspects of child development. In contrast, the influence of fathers was significant regardless of their socioeconomic status. Be they from an affluent city suburb or a deprived rural area, fathers who involved themselves sensitively in their children’s lives had a profound impact on their mental development and language skills. Indeed, in the case of this latter aspect of development – the acquisition of language skills – the influence of fathers was significantly stronger than the influence of mothers. And because of their separate influence, dads were able to compensate for the impact of an insensitive mother on her child’s development, meaning that dad’s parenting skills were capable of buffering his child from the potential negative impact on mental development of having a less than healthy relationship with mum.
It is clear that, as a dad, the power you hold to influence your children’s structural and functional brain development has the potential to provide them with the strong neural foundations that enable them to learn from their experiences and produce suitable behavioural reactions. And one of the key areas in which it can be critical for your children to get these reactions right is in social situations. We know from Chapter Five that all our fathers – Ota, Mike, Sigis and James – were focused on enabling their children to learn about and experience their social environment so that they could develop the appropriate skills to be successful adults. In this chapter, I now want us to understand what it is about the dad’s behaviour and input that enable him to do this.
Adrian: She is very used to being very sociable and stuff, as well, and socially kind of forward. She is gregarious.
Noah: And also she is really likeable.
Adrian: You say that, but you are the parent.
Noah: No, but if she weren’t likeable . . . without a doubt, you know if people don’t like your kid. But that really helps because she is fun to spend time with. I enjoy her company.
Noah and Adrian, dad to Judy (seven)
The offspring of all social animals, like Judy above, have to navigate entry to their social group and take on board the rules that govern behaviour within that group. In lower order animals, such as ants or bees, they do this by using visual and olfactory – smell-based – cues to orientate themselves. In mammals, offspring gain their first social lessons while they are still with their parents; they learn to build a mutually beneficial relationship with their mum or dad. In humans, the knowledge that we need to acquire to cement our social bonds is at two levels. The first is the more basic mammalian level where our
hugs, strokes and kisses release oxytocin, which provides the neurochemical glue for our bond. And then the second is a higher level, where we employ our large neocortex – that’s the folded surface of the brain where our higher intellectual and cognitive abilities sit – to develop social relationships through language and complex thought. In romantic relationships, that’s the doe-eyed daydreaming, sudden urge to write poetry and an inability to stop pondering your love’s myriad good points. And we need to start employing these two levels of behaviour – the hugging and the talking – at a remarkably early age. Once we hit toddlerhood, we begin to move in circles that are not necessarily populated purely by our relatives. Starting pre-school means entering a world where our potential relationships are not underpinned by genetic relatedness, and the benign acceptance this implies, so to make sure we are accepted into this group we need to employ two key skills: the ability to regulate our emotions so as not to scare anyone off and the ability to understand and abide by the rules of the setting – that is, to adopt the social norms.
Ruth Feldman’s theory of bio-behavioural synchrony, which, she argues, is the mechanism that underpins all attachment relationships, implies that there is a relationship between the behavioural, physiological and hormonal measures of two tightly bonded people. But in a groundbreaking study, Ruth’s team has gone on to show that this mirroring extends to the very structure of the parent’s brain. They found that there was a positive link between the density of neural connections – that’s the white matter – in a parent’s brain and their child’s ability to appropriately regulate their emotions and embrace the rules of their social environment.
