I think intelligence starts when the internal system controlling behavior develops a model of the outside environment and operates on it to drive decisions. That is, behavior is not through a simple physical mechanism or evolutionarily refined control system, but by means of general purpose model making.
Intelligence has degrees that begins with any abstraction and ends with arbitrary conscious theorizing and decision making (and a metric of how effective this ability is).
> I think intelligence starts when the internal system controlling behavior develops a model of the outside environment and operates on it to drive decisions.
But isn't that what one of the studied fungi did? To make a decision to grow into the direction where it found food the last time instead of every direction like it did before, it needs to have some sort of model of its environment in its memory, and needs to be able to make decisions based on that model.
Intelligence has degrees that begins with any abstraction and ends with arbitrary conscious theorizing and decision making (and a metric of how effective this ability is).