Where does the continuous floor space rule come from?

[lucyhope]

Hello,
I have been trying to research in term of actual scientific study as well as forum research to try and separate opinions from facts. I don't yet own any hamsters but coming into this the fact that there are about a million different 'minimum sizes' is confusing as the research only really says 'bigger is better' and 'enrichment is important'. Grossly oversimplified, but from what I can tell that's the closest to a factually supported consensus that there is.
I'm just trying to find a study where the one continuous floor space rule was tested. If anyone could help me that'd be fantastic.
Thank you