It’s common to try to explain things as either due to nature OR nurture.

Or, at best, we say: some percentage of the variation in outcome is due to genes, and some percentage is due to the environment. It’s important to remember, though, that outcomes can be a complex interaction between the two.

Consider this:

Our genetically-influenced traits impact what environments we seek out and find ourselves in.

For instance, risk-taking seems to have moderate heritability, and it influences career and life choices that change our environment.

A risk-taker is more likely to seek out riskier environments. And this choice of environment might itself depend on the opportunity set (i.e., current environment). In one environment, risk-taking might mean a greater likelihood of entrepreneurship; in another, it might mean crypto trading, and in a third, drug dealing.

Genetic propensities and the environment we are in can become intertwined.

Consider depression:

Depression seems to have a heritability in the 20%-60% range.

Some are unusually susceptible to it, others less so. Yet whether someone has a depressive episode or not may depend a lot on what environment they happen to be in.

With meaningful work, supportive friends, a robust exercise routine, and effective self-regulation strategies, even with a high propensity toward depression, you may be able to avoid it. On the other hand, if you’re unemployed, lonely, and without helpful routines, even with a low propensity toward depression, you may still become depressed.

So while it can be useful to think about the heritability of a trait, it is important to remember that heritable traits can influence what environment we end up in and that the interplay between genes, environment, and our habits/skills/strategies are what leads to outcomes.

So while it’s common to think in terms of:

(1) nature OR nurture

…or, at best… 

(2) an additive model: outcome = w * nature + (1-w) * nurture…

…Sometimes, a better model has an interaction term:

outcome = w1 * nature + w2* nurture + w3 * nature * nurture.

This was first written on April 28, 2021, and first appeared on this site on December 9, 2022.