Today we looked at a number of the realities present at birth. These are the factors — both within and around the individual — that give rise to individual differences among us.
Think of life as a journey.
All of us, embarking on the journey, come to terms with the human condition — ineluctable dimensions of life in this world that we share in common. We talked about some of those dimensions: that we are embodied, that we have an inner world, and that our nature is social. Another feature of the human condition is that in our lives, from beginning to end, we are involved with intentionality and goal-seeking, and the creation of meaning that gives shape and substance to our exercise of self-agency.
In addition to the commonalities, we have individual differences in where we start our journey, and who we are as we begin.
It’s easy to see that we all start from different places, and that our journey will be influenced by our social ecology: we’re born into different historical times and geopolitical locations, different social/cultural/sub-cultural contexts, different local communities, and different families of origin that include different individuals with whom we will form unique relationships.
Bronfenbrenner’s Social-Ecological Model of Development
Center for Child & Community Development
Southern Methodist University, Dallas, TX
At the same time, we’re born with a set of characteristics reflecting the history of our prenatal (gestational) and perinatal (birth process) experiences, and our genetic endowment.
For humans, genes don’t dictate behavior in any direct way. Some species are born pre-wired with the skills they’ll need to survive; think fruit flies, or baby turtles. Some are born with pre-wiring that is “unlocked” and elaborated by some form of learning early in life. Primates, many mammals, and indeed all social species fall into this category. Humans are the species whose development is most dependent on a lengthy period of learning, training, and apprenticeship that turns them from novices to advanced beginners in the journey of life. In the eloquent words of Gary Marcus,
Innateness is about the extent to which the brain is prewired, plasticity about the extent to which it can be rewired. Some organisms may be good at one but not the other: chimpanzees, for example, may have intricate innate wiring yet, in comparison to humans, relatively few mechanisms for rewiring their brains. Other organisms may be lousy at both: C. elegans worms have limited initial structure, and relatively little in the way of techniques for rewiring their nervous system on the basis of experience. And some organisms, such as humans, are well-endowed in both respects, with enormously intricate initial architecture and fantastically powerful and flexible means for rewiring in the face of experience. (2004, pg. 10)
Almost all the traits of interest in human development are polygenic in origin — dependent on the joint operation of many different elements of the genetic code — and genes’ influence is probabilistic rather than deterministic. The expression of our genetic endowment is the outcome of a complex series of transactions between the individual and the world, or G X E: genes interacting with environment. The study of this process is called behavioral genetics. These sites will introduce you to key concepts in the field.
One more step, and we’ll be ready to look at temperament, the relatively enduring set of characteristics with which we begin life’s journey. Variations in temperament, present at birth, reflect the influence of genetic, prenatal, and perinatal factors, and represent individual differences in how each nervous system responds to environmental stimulation. Genetic sources of temperament exert their influence by shaping important properties of the nervous system — the “initial architecture” to which Gary Marcus refers — as described in this brief overview.
So when we look at dimensions of temperament described by researchers — whether nine dimensions, three, or five — we’re seeing the individual’s nervous system in action, with its specific, characteristic patterns of reactivity. There will be some degree of change in those patterns as a result of experience, since the nervous system is plastic; yet since a person’s temperament both affects the environment and shapes the person’s experience of environmental events and conditions, characteristic patterns may persist over a range of experiences. Wachs (2006) gives a detailed analysis of this interaction, and Kagan (2009) discusses stability and change in one temperament dimension that has been the focus of his research.
A recent analysis depicts the mutual influences of genetic endowment, nervous system reactivity, environmental events and conditions, and behavior. No simple one-way lines of causality here!
Hyde, Bodgan, & Hariri (2011). Understanding risk for psychopathology through imaging gene-environment interactions. Tr.Cog.Sci., 25, 423.
Now let’s look at one treatment of temperament: the description offered by Stella Chess and Alexander Thomas, among the principal investigators of the New York Longitudinal Study in the 1950s. In class we used materials from a website designed to educate parents about child temperament; the specific handout we began to review was called “Tips for Handling Problematic Temperament Traits.”
At our next session, we’ll spend some time with the handout, and then progress to our discussion of resilience in human development. More on that later!
And between now and then . . . shanah tovah u’metukah!