Or maybe it was just the computer version of grasping at straws. None of the future gamestates looked good, so it ended up picking whatever could at least theoretically lead to a comeback, even if that would require Lee Sedol to miss a completely obvious move.
This looks like a possibility to me. I'm not sure that Alphago has any idea how strong an opponent it is facing at any given moment. It's played games against venues and it's played games against professionals. But if a set of complex advanced moves are still likely to lead to a narrow defeat, it might well pick some stupid moves that in theory could allow it to win back a dominant position if the opponent plays badly.Since it doesn't have a model of the competence of its opponent, that might appear to be a viable strategy because against some opponents and in some past games it's played, that could work.
This is really interesting, because forming a model of our opponent and tailoring our strategies appropriately is fundamental to how humans approach competitions.
