Who are we?
The debate whether we begin our lives as a “tabula rasa” (blank slate) verses having our development predestined, be it from God or from genetics is an ancient one. In addition to this, I want to explore the question of how much we can know about who we are. You may have heard of Renee Descartes, a philosopher who famously said "I think therefore I am", ushering in an era of human rationality known as the Enlightenment. Descartes was referring to the amazing ability we humans have for conscious reflection. Certainly this amazing ability is a powerful tool, but modern neuroscience increasingly reveals that, in fact, it represents only a relatively small proportion of who we are.
Our study of human development has revealed that an amazing amount of neural development occurs in bursts over the first three years of human life (including prenatally), well before we are capable of conscious reflection. Here we may begin to explore the evolution of some of the layers of who we are, as they are laid down in a complex dance of inborn potential and environmental feedback.
Neural development, of course, involves all the major structures of the brain, however development appears to occur earlier for certain structures than others. Interestingly, it is the right hemisphere that appears to develop earliest. You may know that we humans have an interestingly divided neurology. We have a cerebral cortex, that highest level layer of our brain, that is divided in two, joined by a remarkably narrow strip of brain matter known as the corpus callosum. Each side of the brain is preferentially connected to the opposite side of the body, but these two hemispheres have also been shown to have very different ways of processing our lived world. A recent work by Iain McGilchrist (The Master and his Emissary) does a comprehensive job of illustrating the implications of this lateralization of human consciousness.
This earlier developing right hemisphere certainly learns, and it certainly thinks, but it's learning and thinking happen implicitly. That is, learning happens through experience and is recalled automatically and unconsciously, leading to changes in our physical states including our emotional states. In human infants the learning and development that occurs first are various forms of bodily and sensory regulation. As you may know from experience, tiny infants cannot yet regulate almost anything about themselves. Unlike some creatures, who can be independent even at birth, humans have some of the most dependent infants in the animal kingdom. Human infants require the constant presence of the caregiver for regulation, and as studies of Romanian orphans have shown, the implications of having little physical contact with a caregiver, even in the presence of adequate food, water and shelter are profound and often devastating. Our emerging genetic potential requires the scaffolding of a human relationship to unfold from the very beginning.
Nature and Nurture
Michael Meaney is a Canadian researcher who has done some fascinating work in the implications of infant mother interactions and the implications for this for gene expression. The word for environmental experiences that influence gene expression is “epigenetics”, and our understanding of this process is only just beginning. These very early interactions appear to be fundamental in the expression of certain genes that have major implications for behaviour and stress reactivity. In rats, the parental behaviour that triggers gene expression is anogenital licking. In humans it is a series of interactions that lay the groundwork for our ability to navigate the sensory and interpersonal world that we will be living in.
Even prenatal development involves more than simple genetic unfolding. We know that stress during pregnancy increases the risk for premature birth and low birth weight, which are associated with various adverse health and developmental outcomes. Some recent studies have suggested increased rates of ADHD, anxiety and mood disorders, although this is a surprisingly under-researched area. Temperament may also be affected with infants whose mothers have been highly stressed showing temperaments at the extreme ends of the spectrum. It seems that genetics does contribute significantly to temperament at birth, determining how an infant may respond to stress, with either increased or decreased reactivity to stimulation.
The first nine months or so of human development involve an incredible surge of brain development. The senses of smell and touch are most important initially, when physical contact are paramount. Vision and hearing then play an increasing role. Here our preoccupation with the human face and voice begin. In particular, the eyes. Babies seek out the face of the mother and an incredible conversation begins. A conversation held with caresses, flashing eyes and playful vocalizations. In this interaction the baby develops an increasing ability and even enthusiasm for processing information. The mother is the guardian of stimulation. It is her job to optimize the amount of stimulation, much of it which will be coming from her. A "three bears" rule of not too little, not too much rule is something the baby manages on his end by seeking, calling and looking away. The mother intuitively responds to these cues from her end. The match between the mothers natural inclination to stimulate, her stress level, and the infants partially genetically determined optimal window of stimulation seems to be key here. This is what some researchers have referred to as “goodness of fit”. This window is a sensitive one and as we know from "Still face" experiments, a period of rupture from this dance of interaction can be very distressing for the infant, who as yet cannot navigate this world of stimulation.
Orchids and Dandelions
Some genetics appear to allow children to develop well enough in a wide range of environments while other genetics lead to high sensitivity which appears to lead to very good outcomes in well matched environments but very poor outcomes in other environments. Bruce Ellis, a family researcher at University of Arizona, coined the term “orchid children” to refer to these highly sensitive children with the more fragile genetic make-up. He referred to the hardier children as “dandelion children".
Introverts and Extroverts
In the first nine months of life the basic ability to regulate stimulation is beginning to develop. Allan Schore, in his series of texts, has compiled vast amounts of interdisciplinary research tracking the neural pathways in the right hemisphere that link our sensory brain to our planning brain and relay directly to our limbic system (emotional, physical control centres) that encode these mind-body interactions which we refer to as sensory-emotional regulation. Do you shy away from busy situations or do you seek them out? Do you detest quiet setting or do you thrive in them? This dance of genetic potential with environmental feedback in these nine months has a lot to do with it. Remember however that mother alone is not responsible for what happens here. Mothers themselves (as you might remember from my last post) are not islands. Their own stress levels are dependent on those around them. The support of fathers, extended family and the broader community has everything to do with the stress level under which any mother will be operating both during pregnancy and thereafter. Our society as a whole has responsibility for how stressful an environment these early years will be.
Change is possible
The amazing thing about development is that although there are important windows, the story if never fully determined. New developments can always emerge and neuroplasticity for change is much greater than we once believed. In the next few posts I will cover some of the next milestones the human infant will cross as we travel this complicated terrain of human development.