For this ignorant one, explain "G".
iirc, "G" is the fundamental "intellectual capacity pool" from which all measurable characteristics (creativity, analysis, etc...) are derived.
I have yet to see a definition of the neurostructural basis of "G" that could be used to compare neurostructural differences between individuals and accurately predict differences in raw intellectual capacity - with the sole possible partial exception of density of syanaptic interconnection within the neocortex.
I suspect that "G" is likely to be found to be bunk as neuroscience trundles along on its current trend of exploding 19th Century notions concerning the psyche and intellect.