"The best laid plans......"

"The best laid plans of mice and men often go wrong" (simple version), is a famous quote by Robbie Burns.
We look at that quote and we can work with it - basically the best-laid plans of men (meaning men and women), often go wrong, we can understand that and most of us can relate to it. However, let's now look at the part that is often overlooked.
"The best laid plans of MICE often go wrong". Has any one actually seen a mouse making a plan? It's not as if we go round our homes and say "oh don't step there, there's a mouse making a plan", and then see some mice with flipcharts and think, "ah these are the best laid plans". So if the best laid plans of mice often go wrong, does that mean that the less well thought out mice plans are better, and if mice just go with the flow they often pull off quite a strategic move?
Did Robbie Burns see mice one day and think – “ah I see mice, they plan, they plan to nick cheese. Oh he’s broken his stick – what a jesse!” (Direct quote from Mr Izzard)
Ok, I know I've pinched this from Eddie Izzard, but I think he has a point.
WHAT MICE PLANS IS HE ACTUALLY TALKING ABOUT?