[Retric]

That doesn’t support your original point. Color blindness is very persistent over time IQ isn’t. Sure +/- 7 IQ points sounds very accurate, but that can be more than a 30 percentile change from two different tests 1 month apart meaning the actual signal is very weak.

You can read papers saying IQ texts on 2 year olds are strongly correlated with adult IQ, but read the details and individual people’s scores varied wildly.

So sure in aggregate it seems consistent, but that’s largely an artifact of test design. Someone with mental handicaps so profound as to be non communicative will consistently score very low, it doesn’t mean much for the general population.