> Typical estimates for adult IQ [from twin studies] found it was about 60% genetic, 40% unpredictable, and barely related at all to parenting or family environment.

I’m surprised to the point of near disbelief that home/family environment (early childhood nutrition, sleep hygiene, psychological support [feeling love, trust, and security, etc.], and schooling support) have little effect.

I wonder if that estimate will change again as we learn more.

Some people such as myself are bad test takers and need to try over and over to figure things out. I was homeschooled and got a 15 on my ACT. I haven't taken an IQ test, but I imagine it would be pretty mediocre.

It took me forever to figure out even the most basic programmatic language features such as for loops, but one common variable that has allowed me to succeed in software development is unrelenting determination. Things start to click the more you dig into the monotony and it gets easier over time.

I'm not dismissing the study, just wanted to throw out there that you can go far with the unpredictable factors of the human brain.