I don't know of an actual paper either. It's rather just a really good anecdote that illustrates the point.

The first time I heard this was actually just in person from a trainer at work. He told this over like 10 minutes or even more as an engaging story. The monkeys went "Uuuuh banana!" each time. Until they didn't ;) That's essentially how it stuck in my mind. Through the Uuuuh banana! exclamation.