It is my current opinion that there exists no neurological basis for Newt to have concluded that Kaiju would have a second "hind" brain. What are your thoughts on the subject?
Pretty much an extended version of this post. Relevant quote:
For a creature the size of a kaiju (many many times larger than any dinosaur), the nerve conduction velocity from the tail to the head would be something of a problem.
To give a concrete example of this problem, let's say a kaiju's tail gets grabbed in combat. For the kaiju to properly react (as in more than just a damage-prevention reflex, although I won't speculate on the nature of kaiju reflexes here), three things have to happen in order: the sensory signals ("tail grabbed") have to travel through the kaiju's nerves from its tail to its brain, the brain has to process those signals and decide what to do, and the motor signals ("move this way") for that decision have to travel out through the kaiju's nerves once again to reach the rest of its body (including its tail).
Those signals can only travel through nerves so fast (thus the term nerve conduction velocity), so bigger distances between the brain and the relevant body parts translate into longer reaction times. As the Precursors scaled up the kaiju, eventually the latency would get bad enough to cause issues in combat. (Imagine a kaiju not reacting to its tail being grabbed until several seconds later, by which point its tail may have already been sliced off.) This latency issue is why kaiju need a second brain.
I don't know what a kaiju's nerve conduction velocity would be, but presumably Newt does (and it's slow enough that the second brain becomes necessary). Based on that and observing kaiju reaction times for different parts of their bodies, he could figure out the presence of the second brain even if he hadn't seen it in reports or samples. The reaction time pattern (increasing roughly based on distance to the closer of two points, rather than one point as expected from a single-brain setup) would give it away.
