https://astralcodexten.substack.com/p/birth-order-effects-nature-vs-nurture

Introduction

Thanks to everyone who waited two years for me to get around to this.

In 2018, thanks to the 8,000 of you who filled out the Slate Star Codex Reader Survey, I discovered that higher birth order siblings were much more likely to read this blog than later-borns:

Source here; thanks to Emile for the graph

That is, of people with exactly one sibling who read this blog, about 72% of those are the older of the two children in their family, compared to only 29% who are the younger of the two (where by chance we would expect 50-50).

This was surprising, because at the time lots of studies had shown there weren't really birth order effects (that is, firstborn siblings had no major personality differences compared to laterborns). I theorized that maybe for some reason it was easier to find by looking in a heavily-selected group of people and asking members about their birth order, compared to getting a random sample and trying to correlate birth order with things. Sure enough, later amateur research revealed strong birth order effects in physics Nobelists and great mathematicians (and potentially Harvard philosophy students). Given that readers of this blog are highly-educated (about 37% have masters or PhDs) and mostly in STEM (41% programmers of some sort), plausibly birth order affects something about intelligence, education, or STEM orientation (somebody should check literature and peace Nobelists!)