Is the premise that while the effect of birth order on mean intelligence is small, we can see it magnified among our community members and in great mathematicians because each group is likely far more intelligent than average?
I recall reading this https://putanumonit.com/2015/11/10/003-soccer1/, which demonstrates that small mean differences will have outsized effects on groups comprised by the distributions’ tails.
Surveyed! And for the first time, too. This survey was pretty interesting and definitely not what I expected