Actually it means a 3 year old pig is smarter than a 3 year old human, thus is something my mother told me, so I can't really give you the source, but here are some sources I just googled: http://www.pbs.org/wnet/nature/episodes/the-joy-of-pigs/smart-clean-and-lean/2126/ http://www.specialtypettraining.com/graphics/articlepig.html http://www.relfe.com/wp/animals/pigs-cleaner-smarter-dogs/