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by jackcarter 3939 days ago
Dolphins found a way to con a similar system:

"When people drop paper into the water she hides it under a rock at the bottom of the pool. The next time a trainer passes, she goes down to the rock and tears off a piece of paper to give to the trainer. After a fish reward, she goes back down, tears off another piece of paper, gets another fish, and so on."

http://www.theguardian.com/science/2003/jul/03/research.scie...