I have written before that it seems strange that there should be any significant
difference in Intelligence amongst humans with the same brain capacity. Owing to the fact that, evolutionarily speaking, the brain is an extremely expensive organ and it would seem a strange waste to not optimise the software running the hardware. Evolutionary pressure should have dictated that brains be virtually the same, in terms of intellectual capacity, amongst various human specimens.
We know that when we are anxious that it's hard to think normally. In fact with enough anxiety we can hardly think at all. Why? Because most of our conscious attention is focused on external and immediate threat-detection, and in preparation for our anticipated response. So anxiety can and does dominate the metal budget in practice. I notice that I myself am always more intelligent--in an academic and reflective sense--when left alone in a peaceful environment. This is because my threat-detection system is nearly completely off, giving me my mind back in full.
So what has this got to do with IQ? Some people, and probably all of us to a degree, are in a permanent state of alerted threat-detection. We can never fully relax and in turn focus like we should. For some people the threat-detection function is locked-in epigenetically. The result is that threat-detection won't turn off, no matter where they are.
Mothers who are anxious while carrying are more likely to produce offspring that are Attention Deficit Hyperactivity Disorder (ADHD). To be simple, an ADHD individual has been taught within the womb to expect to be born into a dangerous world, and they have been taught this by the mother's emotional state. A baby literally reads the world it will be born into through the mothers feeling-state, and in turn genetically adjusts itself to the anticipated conditions. The womb is a profound primer for the future life.
Will this affect the child's ability to engage in immersive concentration, and in turn compromise their development and operational IQ? Of course it must. But with epigenetics, again, the difference is locked in. So you can't facilitate concentration by simply changing the environment.
Insofar as this is the case, we can see that what sometimes looks like genetic differences in intelligence may actually be environmental; meaning, the environment of the womb. Our assumptions on inherited intelligence being genetic, are based on identical twin studies of infants that have been separated at birth - not separated before birth. In turn, an anxiety-state passed on down through the generations may be falsely representing the real intellectual potential of any given select group of people.
Insofar as anxiety, and its response, compromises operational intelligence we can see that it would make sense to support mothers while they are pregnant. This is to be sure they do not expose themselves and in turn their babies to any more anxiety than need be. That would be easier said than done if the mother is inherently anxious due to her personal history, but we can do our best to make things better for the child nonetheless.
Note: I would like to add a practical note for employers: Making your staff anxious is no way to get the best out of them. You're more likely to turn high-IQ into high staff turnover, and you can only get away with that (without cost) on a mindless production-line. And this problem, where it exists, is easy to solve. Just talk to your staff about how they feel around you, their supervisors, and their co-workers. As I've argued in this article, how they feel is in fact a very important question. You want to know if you're making your staff "dumb". And speaking from personal observations, this problem happens all the time. It's amazing how many employers create the very problems they try to solve by breathing down their staffs necks, subtlety degrading them, and making them feel anxious.