[G]enes and environments constantly influence each other throughout a person's life. This principle actually has two parts. First, genes are expressed - "turned on" - throughout the life span. [...] Second, the environment can trigger genetic expression: A person's experience can help to determine how and when genes are activated. [...]
Genes can influence the kind of environment to which a person is exposed. In other words, "nature" can help determine the kind of "nurturing" that a child receives.
The concept expressed here, and elsewhere in this week's material, is that these factors (a child's genetics and phenotype, their parents' genetics and phenotype, and the environment in which the child's development takes place) are all interconnected and exert constant influence on each other. There is no isolated cause-and-effect relationship, but each element has a causal influence on all others. Sure, genes can't be changed, but they can be activated; nature and nurture are constantly modifying and modulating each other.
This week's material contextualizes this idea within early development, but it's clearly an ongoing process throughout a person's life. We are our genes, and we are also the environment in which the genes are expressed. The interplay of these factors is constantly progressing and evolving. For me, today, at age 35, the process has slowed somewhat. Genetic traits that had any chance of expressing in my personality have, by now, mostly done so. An adult is less malleable than an infant, and I suspect it's not only due to an infant's mass of unconnected neurons that this is so. As we age, the environment-genetics interplay is joined by a third factor: experience.
The weight of a person's experience is not discussed much in this week's material - again, we're focused on pre- and post-natal development. But for me, right now, I am still experiencing the overlapping influences of my genetics and my environment I did as a child, but I am now also a creature with memory. I know who I have been, and I know the choices I have made over the course of my life. This effect increases as I age; experiences that I have now might recontextualize experiences I had as a child, but they don't change them. This is the Life-Course Perspective view of human development discussed in the previous chapter. This is the increased continuity. Babies are more subject to sudden shifts in temperament and development because they don't have the cushion (or the burden) of experience to modulate the effects.
This is only in true part, of course; a baby's brain is biologically less set than ours. But I wonder - how much of this early-life development is duplicated by adults who suffer severe memory loss?
- Ben
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