http://www.golfdigest.com/instructio...psexcerpt.html
http://www.golfdigest.com/search/ind...ttingyips.html
There was a study done some time ago that identified the eyes jumping around in their sockets as characteristic of the yips. Some advocate moving the eyes to the leftmost part of the socket before putting. Your head straight down, eyes straight down, ball forward...then shift eyes left in their sockets to see ball/line before startup. Might be worth a try if it fits into your putting style.