3 Laws of Behaviour Genetics

Genetics

[EDIT: Researching immediately after I wrote this article, I skimmed—I’ll have to find time to read it later—Turkheimer’s paper Still Missing (PDF, 2011), where he walks back his original assertion.]

The question, “why are children in the same family so different?” is answered, “Because measurable differences in their environment make them that way.”

I finished Pinker’s The Blank Slate the other day, but I didn’t have much time to capture my reflections. I’m already onto my next book, Mill’s Utilitarianism, so I figured I record some thoughts before they become too distant.

In chapter 19, Pinker summarises Eric Turkheimer’s paper Three Laws of Genetic Behaviour Genetics and What They Mean (PDF, 2000):

  1. The First Law: All human behavioural traits are heritable.
  2. The Second Law: The effect of being raised in the same family is smaller than the effect of the genes.
  3. The Third Law: A substantial portion of the variation in complex human behavioural traits is not accounted for by the effects of genes or families.

Elaborating on this, he summarises Turkheimer’s assessment on the variance in personality contributable to three factors: genetics, society, and family. According to this theory, variations in personality due accounted for by environment, are composed as

3 Laws of Behaviour Genetics

50 percent accounted for by society (non-shared environment); 40 – 50 percent accounted for by genetics (biology) and 0 to 10 percent attributable to family (shared environment). In his assessment, he was able to eliminate usual-suspect factors like birth order and siblings.

“Genotype is in fact a more systematic
source
of variability than environment.”

According to Pinker, the 0 to 10 percent is generous, and it could just as well be 50% society and the rest is genetics. That doesn’t leave a lot of room for psychoanalysis, a discipline who strongly pushes back on this concept—just with emotional appeal in lieu of science.

Post-Post-Modern Subjectivism

I’ve just finished reading Steven Pinker‘s The Blank Slate. Originally published in 2002 (and re-published with an afterword in 2016), it still feels fresh. Pinker offers compelling rationale for accepting that humans are not blank slates entering the world.

Though I am somewhat of a social justice warrior in principle, I am still a moral subjectivist, a post-modern thinker. Pinker shares his strong feelings against subjectivism, but he provides no evidence of the moral objectivism he advances, relying instead on an emotional appeal; in fact, he employs the same defensive tactic his detractors employ, which is to try to make an empathic connection to the reader.

All he does is to claim that there is an objective morality because everybody feels and knows that X is better than Y, taking a strawman approach. It’s not that I disagree with his Xs and Ys; it’s just that they are subjective not objective measures. He tries to slip in an appeal to popularity by claiming that everybody would (or should) feel this way when push comes to shove.

Nietzsche, I think, had it right in Beyond Good and Evil when he pointed out the dual moral systems of masters and slaves. Although a moral (just) system might be best constructed from scratch in the manner of Rawlsveil of ignorance, we are not starting from a blank slate. The power structures are already in place. There is a possibility for upward and downward mobility, but large jumps are not likely except in the manner of a lottery. Other than this, it’s unlikely that one will move from one quintile to another and even less likely to skip a quintile, especially on the upward trend.

In any case, the issue is not whether some might feel subjectively better; it’s whether—across all possible dimensions—a relative, stable equilibrium can be found. Even here, this is not objective, even if it’s not otherwise arbitrary or capricious. The larger problem is one of epistemological empiricism—apart from the ontological question—, whether we can know that we’ve found the objective truth or if we’ve just settled on something that works for our current station.

As much as I really do like Steven Pinker, and I await his next book, Enlightenment Now, I do so only to read how he couches his argument in support of Enlightenment and Humanism, two concepts I feel are tainted by hubris