This example shows more, that brain-neurons and the overall system "brain"
does not work like a computer.
There is a very fuzzy decisionmaking, and no binary approach.
So the donkey will not get a "Systemerror, cant differentiate between choices".
Thus the behaviour of the donkey can not be predicted.

But he shure will not starve...

but how do you know that? have you tested that?

i know the answer:

function choose_stack
{
randomize();
chosen_stack=int(random(2));
}

easy as that