http://www.eecs.harvard.edu/~yaz/en/squirrel_fishing.html

Another question that has been puzzling researchers for years is whether it is possible to make a squirrel fall on its back by skillful manipulation of a bait suspended above its head. The theory was that this could be achieved if this bait was moved in a straight line over the center of gravity of the squirrel towards its back.

After many hours of experimentation, we were able to disprove this theory. More research is needed to determine if squirrels get dizzy from prolonged spinning around.