Pet tricks are brain games; like Sudoku for dogs

Lexington, KY - "Animal tricks -- stupid or otherwise -- were not invented by David Letterman. Indeed, the Medicis -- over-the-top dog people, even by Renaissance standards -- supposedly had a dog that cleared the dishes and poured vino without spilling. And arguably for as long as dogs, cats and other creatures have shared our hearths, humans have delighted in any behavior that offers a glimmer of kinship..."
Source: Kentucky.com, 2/23/2006