Not at all a scientific finding but: when I was out of college, years ago, I spent a summer doing mobile vet assistance work. Every weekend we went through small and large towns through Oregon, Washington, Idaho and northern California. This is before Petsmart and so forth existed. I was in *a lot* of contact with all kinds of dogs...more so than a regular vet, because the company I worked for would send out flliers beforehand and advertise the low-cost vaccine program a week before we arrived.
Anyway...there were two times of all those dogs that I was bitten or almost bit...both times were chessies. Just putting that out there.