Why should intelligence _other_ than motor-planning be tied to the degrees of freedom of their movement?

- snakes have a high number of degrees of freedom but aren't especially bright

- squid have 2 more limbs than octopuses and aren't as smart

I think the shallow-water vs deep-water thing mentioned in the article is important; reef and similar environments give a lot more opportunities for smart camouflage, complex navigation, tool-use opportunities etc than the open ocean.

the history of how people have conceived of causality between human intelligence and human hands (and in which direction dependency may lie) is quite interesting. "It is by having hands that man is the most intelligent of animals." —Anaxagoras, circa 450 BCE.

most likely the enormous control surfaces their biology acquired required distributed neuronal mass and once that mass existed further intelligence became advantageous because it was a minor change at that point (switches during embryology increasing neuron counts and other aspects).