[Natanael_L]

One guess is that our brains are "lazily" allocating neurons to tasks, since we have so much space available compared to most animals. The signals are simply allowed to branch out / propagate much further (and redundancy is probably involved too). The paths are simply built where the signals goes.

But when it is constrained, and there's still enough of all the important brain structures, the density (interference?) of different signals probably causes them to propagate much less such that the processing of each signal will get processed by fewer neurons, and the same functions are still achieved.

Kind of like a space optimized FPGA design vs a lazy one that uses all the logical elements because there's no need to be compact.