Nature, nurture and friends

If life gives you lemons, what should you make?

2015-06-05 — 2025-07-13

evolution
gene
semantics
Wherein the heritability of traits is examined through twin studies and variance decomposition, and the influence of shared environment, genomics, and causal inference methods is surveyed.
Figure 1

Nature! Nurture! Another distinction that sounds like it might represent something. Fundamental And Real and Unambiguous. Has supplanted Calvin’s distinction between total depravity vs penance in the people-blaming niche.

I don’t have much interest or expertise in this area, but this placeholder will collect a couple of interesting links to refer to next time I get caught up in some aggravating vague semantic argument about inheritance of things.

See also other quirky taxonomies:

Unlike Doctor Who/Daleks, this one is used for actual decision making and public debate outside Tumblr, so it’s worth looking into.

1 Which is more important, nature or nurture?

At risk of weak manning I think we can rule out the usefulness of this question as it stands, which I presume few actual researchers ask. We need to refine it to get to an answerable question. That should go without saying, we would have thought, but pub conversation suggests not. To recycle a common analogy, imagine a computer science where the central questions were ones like: “Can I do word processing on my laptop because of hardware or because of software?” This kind of muddy thinking will have us trying to discern the contribution of “hardware factors” versus “software factors” to word processing via a variance decomposition. Not that variance decompositions usually happen in pub conversations. Anyway, we get the drift. To say anything useful we must make sure it’s clear what we are getting at; that seems challenging in this area for some reason. (Probably: because this politically charged topic looks simple enough to have an opinion on.)

1.1 Heritability scores

The classic heritability score.

Spoiler: Heritability is a variance decomposition over two factors. This is a reasonably blunt instrument we can use to bash results out of meagre data and computation. Many studies — e.g. twin studies — are constrained by lack of data because there aren’t many twins. This might change with advances in genomics. As with any observational research, we should be suspicious of studies that don’t at the bare minimum extend their methods to a causal DAG and make the right interventions to estimate what we actually wish to estimate.

Homework questions for classic heritability scores:

  1. How heritable is vocabulary size?
  2. How heritable is bank balance?
  3. How heritable is a bachelor’s degree in evolutionary psychology?

1.2 Incoming

  • If everything is genetic, then nothing is genetic

  • Ozymandias, Shared environment effects are real makes some interesting points about how we discuss shared environment.

    Believing in zero role for shared environment also fails to pass the sniff test. Lots of people, I think, will agree that whether or not you talk to your baby might not have any long-term consequences. But the “zero role for shared environment” position requires yourself to commit to the position that all of the following have either zero correlation between siblings or no effect on children’s psychology whatsoever:

    • Lead poisoning.
    • All other forms of air and water pollution.
    • Prenatal nutrition.
    • Drinking during pregnancy. […]

  • Scott Alexander parodies The Gattaca Trilogy

  • Jeffrey Lockhart’s Blueprint for what is a fairly adversarial review of an evolutionary psychology book, and it covers some of the weak-manning that happens in this debate.

  • Jay Joseph has a beef with MISTRA, an important twins study, especially as it bears on IQ. As far as I can tell, this hasn’t survived peer review?

1.3 Evolutionary Psychology

Based on this review, I would like to read Anne Innis Dagg’s “Love of Shopping Is Not a Gene,” for some evolutionary psychology amusement.

My favourite Evolutionary Psychology slapfight, because it is dead earnest, is the In Our Time Episode, where Melvyn Bragg is in magnificent form, with scientists rambunctiously talking past each other in a microcosm of evolutionary psychology discourse more broadly.

Bahfest is also neat. It can be hard to tell satire from earnestness in this domain, as per Poe’s Law. For example, is Charlton (2014) a brilliant mockery or abysmal science?

1.4 Incoming

1.5 References

Charlton. 2014. “Menstrual Cycle Phase Alters Women’s Sexual Preferences for Composers of More Complex Music.” Proceedings of the Royal Society B: Biological Sciences.
Joseph. 2018. “Twenty-Two Invalidating Aspects of the Minnesota Study of Twins Reared Apart (MISTRA).”