Someone mentioned what I think was referred to as 'logical distance'.
My hard drive crashed and I dont have the link anymore.
I do recall that I ran across it on this site, in response to linking algorithmic complexity to information theory.
It was a link to a University of Chicago researcher, and dealt with this field. I think also that computational neuroscience people use it.
Tried searching online and here but no luck.
If this rings a bell for anyone please direct me to that topic.