I think early stimulation has the most to do with it. Plopping a baby in a bouncy seat or a swing and putting an Elmo video on is not stimulating a baby.
Having a crack mom bring you into this world probably does not correlate well to healthy brain or cognitive development either.
“Half were from low income homes, and half from high income families.”
If this was the ONLY CRITERION for measurement, the study would be considered invalid.
Is this post a joke or ?
The joke would be on the people who were contributing salaries (ie: money) for the experimenters doing the “study” - and it could have been done at taxpayers’ expense.
Now the group is making more money publishing their results.