Has there been any work on designing a proof-of-work algorithm dependent on HITs (Human Intelligence Tasks) ?

An example could be a proof-of-work scheme based on captcha solving. (Assume computers can't solve captchas. Obviously there are captcha-solving systems that work without human intervention.)

The HITs would need to be such that humans are much better than computers at completing them. There might be a mathematical puzzle that reduces to suitable HITs. Those HITs could be presented to humans in a game interface in a client app. Alternatively (maybe no such puzzle is found), there might be some informal HITs that could be verified through a voting system. Another idea that popped into my head is that a challenging game such as Go could be implemented into the protocol of a cryptocurrency, and beating a highly rated player would count as proof-of-work.

EDIT:
Here are some potential reasons such a PoW protocol could be valuable:
1) If enough people were to participate, even money and computational resources would not be enough to do a 51% attack.
2) The HITs could be implemented into games. The games could get a share of mining proceeds.
3) The HITs could be useful, creating a distributed crowdsourcing platform.