I disagree with their theory.
While hormones are part of the process, they are not the ultimate director of such processes.
The terms ‘genius’ and ‘very bright’ are not exactly measurable quantities, and not necessarily the same thing.
It is my belief, based on looking around me, that those who are tagged as ‘genius’, usually are deficient in other areas (mentally).
They either have a physical reason to focus (Steven Hawking) all their mental abilities into one channel, or they achieve focus in one area, by not using it in any other area (absent-minded professor, weirdo geek, etc)
Then there are those who are autistic. Very bright, highly non-functional in society. The cause is a toss up, but the methodology is the same. The mind concentrates it’s power in a limited area permanently, by abandoning others.
There are plenty of highly intelligent (say...based on MENSA scores) ‘normal’ people out there, who COULD be ‘geniuses’ if they focused all their attention to one thing, at the expense of the others. But, they don’t.
To conclude, Hormones may be an ingredient of the ‘cause’, but it is only one among many.
I agree with your observations.
Indeed...but the power to concentrate and focus is undoubtedly (largely) genetic.