Originally Posted by Fazor

I'd suspect it has less to do with head size, and more to do with the inbreeding that goes on to keep them "purebred" and maintain high "performance" for racing. Same problem with dalmations...and I suspect any other dog that is prized for it's pure-bred-iness. (We had a dalmation growing up, though my parents only put up with it for a year or two. It was dumber than a brick.)