how can computer games learn?

Ok, before I get in trouble from everyone telling me how stupid computers are, there are a few games I can think of that do, in a way, learn from people. For example, the AI on Super smash bros Brawl for the Wii will "learn" to some degree and actually adopt the techniques of players. If you use one move too much, the AI will later start spamming that move, if you start using some more advanced techniques, the AI will start using them. If a really good player comes and plays the game at your house, the AI for the character they used will become 5x better than it was before (which is why a lv 9 Ness is now almost impossible to defeat on my system). How on earth did the programmers manage that? Is this "learning" or is it something else. What else can they program a computer to "learn"?

 

http://en.wikipedia.org/wiki/Machine_learning

 

Best way AI can learn is a neural net, but it's kinda complex to set up (not to mention hit & hiss), so most games have hardcoded rules instead.

 

Why out of all methods is that the best?

 

Mario via AI evolution

Very simple AI learning, but it does work. If some random guy working from his basement can make this, a dedicated, professional group can do wonders if they're given the proper commercial support.