[mr_toad]

> why a mouse is intelligent but an ant is not

What makes you think mouse intelligence is fundamentally different from ant intelligence?

It seems as if you’re assuming some sort of structural break somewhere between very simple neural nets and more complex ones, which is basically begging the question.

[Veedrac]

There clearly is a change in structure somewhere, even if the precise location is arguable, since extremely small brains are fixed in structure (every connection is deterministic) and seem to implement completely fixed programs.

I imagine the transition will be fairly fluid, with ants running a mix of sophisticated hardwired programs and more simple learned associations (and even humans having a degree of fixed-function behaviours), but that's not to say a distinction can't be made.