However, see earlier post, the current idea is that it is neuron density rather than brain size which determines intelligence. (or it's brain cell density--it's density of some sort--going to look....).
Seems to be both general brain density (brain cells) and neuron density.
Density ~ as in “Belgium is the most densely populated country in Europe” ~ which, in French, cutely comes across as “the Belgian people are really stupid”.