I began by laying out the larger project of Pinker’s book, The Blank Slate. Although I had a few quibbles with the details, its connection with our theme is obvious.
Then we talked about a specific chapter from the book concerning child development.
We closed with a quick survey: what behavioral traits would you say you got from your parents? We’ll use that to see how far Pinker’s theory really challenges what we believe.
Pinker, drawing largely on Judith Harris’s work, claims that most of the variation in child development is accounted for be genes or environmental factors outside the home. Harris proposed peers as the environmental factor. Pinker liked that because it seemed to fit with his observations of language usage. But studies of twins suggest it might not be true.
The most important part of his argument has to do with studies of twins raised in separate environments. It’s easy to observe that parents are like their children. We commonly attribute this to the fact that parents raise their children to be like them. Maybe that’s true. But it’s also the case that parents share a lot of genetic material with their children. The observed similarity between children and their parents doesn’t favor either the genetic or the environmental explanation. For that, we need to split the two factors apart.
It just occurred to me that with cheap genetic testing, we’ll be able to do a different, more broadly based kind of study. There are lots of kids growing up with at least one adult who isn’t their genetic parent. To put it in the lingo of social science, there are a significant number of “non-paternity events”. To put it more crudely, there are a lot of men raising children who aren’t their own … and who don’t know it. About one in thirty.
That fact should help out with the question of the relative influence of genes or environment. If children who are the result of a “non-paternity event” act more like their “fathers” than a random kid would, that would suggest that environmental factors are important.
The most important part of this chapter in our discussion was its definitions of the behavioral traits that, it claims, are either inherited or learned outside of the family environment. If we’re saying that genes account for 50% of the variance among children, we have to answer the question “variance of what?”
I liked this chapter because it uses what Pinker characterizes as the new sciences of human nature to tell us something other than received opinion. Why is that such a good thing? Well, as we saw with Darwin, there is a long history of finding human nature in the peculiar opinions and habits of one’s own part of one’s own culture. So it’s reassuring to find something that swims against the tide.