Do the Four Laws of Behavior Genetics Matter?
Spoiler alert: Yes
This is the fifth and final installment in my series on the Four Laws of Behavior Genetics. You can access the full collection here.
In Parts 1 to 4, we looked at Laws 1 to 4. In this part, we’ll change gears and ask: Do the Four Laws of Behavior Genetics matter? They’re interesting, certainly. But do they have any practical implications for people’s day-to-day lives?
The End of Nature and Nurture
The nature-nurture question has captivated people since at least the time of the Ancient Greeks, and perhaps since we first evolved our capacity for abstract thought. It’s one of the deepest questions that human beings have posed to themselves about themselves. And after thousands of years of treading water on the issue, we’ve suddenly basically solved it. With the advent of twin studies, adoption studies, and other such methods, the nature-nurture debate is now over.
It’s not just that we’ve finally concluded that it’s a bit of both; the smart money was always on that. Instead, we’ve come up with a body of knowledge that’s not only reliable and replicable, but also in many ways surprising.
Some of the most reliable, most replicable, and most surprising findings have been captured in a set of generalizations known as the Four Laws of Behavior Genetics. We covered each of these in an earlier post. In case you need a quick recap, though, here they are one last time.
Law 1: All traits are partially heritable - including even weird stuff like political views and mobile phone use.
Law 2: The effect of the shared family environment is smaller than the effect of the genes. In fact, often the shared family environment has no effect at all.
Law 3: Much of the variance in psychological traits is not due to either genes or the shared family environment. A big part of it is random developmental noise.
Law 4: Complex traits are shaped not by one genetic variant or a handful, but by many hundreds or thousands of genetic variants, each of which has close to no effect.
What Does It Matter?
To my mind, the Four Laws of Behavior Genetics are among the most fascinating discoveries in psychology. Who would have guessed that every trait is heritable - not just some or most, but every trait? And who would have guessed that people who grow up together are little or no more similar than they would have been if they’d grown up apart? These are deep and counterintuitive truths about the nature of the human condition, solving a mystery that’s enthralled us since the dawn of time. It’s hard to imagine how they could fail to be fascinating.
The question I want to address in this post is this: Are the Four Laws of Behavior Genetics just fascinating? Or do they also have practical implications?
I mentioned in the last post that, in the future, it might be possible to use our growing knowledge of the genetics of mind and behavior to identify individuals with predispositions to educational, medical, or psychiatric difficulties, and to create personalized interventions to help them. It might even be possible one day to remove disease-causing genes from people’s genomes. None of this will happen any time soon, but my guess is that it’ll happen eventually.
But that’s not the issue I want to tackle in this post. Rather than focusing on technological applications in the future, I want to ask whether the Four Laws have practical implications for people today. Can this body of knowledge help us to lead better and happier lives?
Many would argue no; after all, we can’t change our genes, so the main lesson of the Four Laws would seem to be that we’re stuck with what we’ve got. I disagree. In my view, the answer is an unequivocal yes. To make the case for this position, let me give you four examples of practical implications of the Four Laws from a range of different areas.
1. Calling an End To the Blame Game
The first implication concerns the allocation of blame. In the bad old days, people routinely blamed psychiatric disorders like schizophrenia and autism on parents, and in particular on mothers. Schizophrenia, for instance, was blamed on schizophrenogenic mothers: mothers who put their kids in double binds by being cold and rejecting but also overprotective and even seductive. Likewise, autism was blamed on refrigerator mothers: mothers who were emotionally cold toward their kids.
These suggestions would obviously have been hugely upsetting to the parents: Not only did their child have a serious psychological disorder, but they themselves inflicted it on them. Still, upsetting or not, if the suggestions were true, this would be something we’d have to confront in our quest to make things better.
The problem, though, is that they weren’t remotely true! Twin and adoption studies have shown beyond any shadow of a reasonable doubt that conditions like schizophrenia and autism are heritable, consistent with the First Law of Behavior Genetics. More than that, they’re highly heritable: among the most heritable traits in psychology.
In addition, to the extent that these conditions are shaped by non-genetic factors, the shared family environment is a minor contributor at best. Twins raised in the same home are no more and no less likely to develop schizophrenia or autism than those raised in different homes - a good example of the Second Law of Behavior Genetics.
Long story short, it’s not the parents’ fault. The more we’ve learned this lesson, the less we’ve unfairly blamed parents - mothers in particular - for these conditions, and the less we’ve caused them entirely unnecessary guilt and anguish.