Size does not matter.
Once and for all let’s put that debate out of the window. Current case in point, bird-brains.
The size of a parrot’s brain is the same as an unshelled walnut while that of the common monkey is as big as a lemon. Nonetheless, the parrot has more neurons in the area linked with intelligence in it’s tiny brain than a monkey!
Did you ever think that science would validate birds are freakishly more intelligent than primates? Clearly calling someone a ‘bird-brain’ is not a zinger of an insult it once used to be.