Are there any games that contain a machine learning AI?

Can anybody here give a reference to commercial AAA games that implement a machine learning AI?

Answer

The most common approach is to train the AI off-line or pre-release, and to ship that final result. As such the game arguably doesn't contain a machine-learning AI.

This is because machine learning can traditionally take many hours of training to produce a usable result, and as it's by definition emergent, it's probably a good idea to put any result through a full QA pass to make sure there aren't any exploitable edge cases.

For the above reasons, and because gameplay changes and balancing even late on might mean that the AI has to be retrained and retested, not many studios use this approach.