Top 10 Most Replicable Findings from Behavior Genetics, Part 2: Findings #6-10
Behavior genetics gets weird
In Case You Missed It…
What if upbringing matters far less than we think, and the environment is shaped in part by our genes? What if many familiar “environmental” effects aren’t really environmental at all?
These ideas might strike you as counterintuitive or even obviously wrong. But they’re not just random hypotheticals. They’re among the most robust and consistently replicated findings in behavior genetics - a field that’s produced some of the strongest results in all of psychology.
In this post, I finish outlining the Top 10 most replicable findings from behavior genetics, first identified in a classic paper by Robert Plomin and colleagues.
And I ask: Why have these findings proved so unusually robust when so much of psychology has failed to replicate? What’s the secret sauce?
If you’re interested in what bedrock looks like in psychological science - and in ideas that might quietly reshape how you think about human nature - this post is for you.
6. Psychological Stability Is Largely Genetic
Why do people remain recognizably themselves over the years? Why do smart people tend to stay smart, shy people tend to stay shy, and depression-prone people tend to stay depression-prone?
Behavior genetics provides a clear answer: Psychological stability is largely due to genes. The same genetic influences tend to operate across the lifespan, helping anchor individual differences over time.
Psychological change, in contrast, is more often environmental in origin. New experiences, new life events, and shifting contexts nudge around our psychological dispositions in ways not directly predictable from our genes.
The fact that genes explain psychological stability rather than change might sound obvious, but it’s not. Genes don’t just switch on at conception, then remain active till the last days of life. Many remain dormant until needed at puberty or other key life junctures. In principle, then, genes could help explain psychological change as well as stability. As it happens, though, they generally don’t. For the most part, stability is genetic, whereas change is a function of the environment.
7. The Environment is Partially Heritable
Now things get really interesting.
Not only are all psychological traits heritable, but the environment is heritable too. Even variables we think of as entirely environmental - parental treatment, social support, major life events - are shaped in part by our genes.
How can this be?