I think some engines learn. A very long time ago I was playing my favorite opening against a chess computer. After a month or so the computer started to avoid that opening.
Now this was one of the early chess engines and I do not know the situation now.
I recently bought Chessking2 with the Houdini2 engine. I played it a little set on 1900 strength in blitz to work on my openings.
I noticed that when I played the second day, it started changing the lines it played to specifically respond to the openings I had been playing.
Does anyone here know about the programming? I was wondering if it's just randomness programmed into the engine, or if it is programmed to respond to the openings I have previously used that are stored in the database. It doesn't apper to be random as the changes have been seeming to meet my opening ideas head on.... Anyone know what's up?