Is 3.1 points small? Well, a 100 IQ is higher than that of 50% of the population, while a 103.1 IQ is higher than 58%. Adding 3.1 IQ points to a kid ranked 13th in a 25-person class would push them up to around 11th. And, personally, if you were going to drop my IQ by 3.1 points, I would not be super stoked about it.
And remember, 3.1 points is still just the impact of a modest increase in breastfeeding intensity. If you ran a trial that compared no breastfeeding to exclusive breastfeeding for 12 months, the impact would surely have been much larger.
For context, in high-income countries lead poisoning is estimated to have lowered IQ by a comparable amount (the paper doesn’t explicitly state the IQ drop, but does say that the mean blood lead level in HICs is 1.3 μg/dL and provides the chart below), and lead poisoning is taken pretty seriously.
For context, in high-income countries lead poisoning is estimated to have lowered IQ by a comparable amount (the paper doesn’t explicitly state the IQ drop, but does say that the mean blood lead level in HICs is 1.3 μg/dL and provides the chart below), and lead poisoning is taken pretty seriously.