

Overjustification effect - parallel
http://en.wikipedia.org/wiki/Overjustification_effect

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mark-r
Reminds me of the children's book "Something for Nothing" which took the
principle a step further. When some cats started trashing a dog's house just
for fun, he offered to pay them to do it. The next day he paid more but made
them work harder for it. And again etc. Finally he said he had no more money,
and the intrinsic motivation of the rogue cats was gone - he never saw them
again.

