It's not about inventing some intangible or non-factual reward.
Perhaps if I frame the carrot thus:
Simply educate people on the wonders of nature, the way science uncovers these wonders and the value of questioning everything. Hopefully they will start to understand that knowing things is far better than being told. They might follow the logical path to questioning the basis of their own beliefs and if they stand up to any scrutiny.
I think educational programs like Cosmos are excellent 'carrots'. Carl Sagan presents a beautiful picture of our existence and how we came to know what we know through the scientific method. He then goes on to ask questions that the viewer can ponder in their own time.
http://www.youtube.com/watch?v=XfMZ76gP61k
Nature is pretty astounding when one gets an insight into how much we know about it (and how much we still have to learn).