(I translated this article written by Lee Sedol himself, which originally appeared on March 18 on DongA.com news http://news.donga.com/3/all/20160318/77081148/1 I tried to avoid liberal translation, so the translated sentences may be a bit rough. I will translate subsequent articles when I have time.)

“Intimidated by AlphaGo’s Reading Becoming More Accurate…”

Lee Sedol’s Review on the Week with AlphaGo <2> Overconfident 2nd Match

After I lost the first match, many thoughts came to my mind. I could not figure out AlphaGo’s habits, which alternate a strange move never seen in professional matches and a move that only top pro players play. However, I felt that I should not judge the ‘strange’ move as bad. I thought there was a meaning, because AlphaGo places a move calculating win probability for each move.

As in the first match, I entered the room with my daughter Hyerim. I felt stable when I was with her. However, I still felt tension during the match.

In the second match, in which I played white, black played a strange move (△) and a move much praised as of top-class intuition (◎). I tested AlphaGo’s skills, recalling the experience from the first match. Seeing black’s move (△), I felt a little bit that AlphaGo likes to pick a shape and go for it.

AlphaGo, which played black, played aggressively in the bottom left at the end of the opening. It must play aggressively to raise its win probability, taking account of its 48% win probability playing black.

However, I thought her strategy was impractical. I thought my chance to win was good.

However, feeling too good, my play had become relaxed. In the match, I cut with white 1, and it was careless. I should have played a dansoo(atari) like ‘가’ first. People who do not know baduk much may ask if it makes any difference, but it is different in a professional match since a small difference decides victory.

I was careless, because without enough reading I thought the white 1 was sufficient while being aware of an atari option like ‘가’.

Personally, I think this move decided AlphaGo’s victory. Other professional players said that the game was still advantageous to me, but I think the flow was opponent’s because I could not win any points in a situation that can be certainly advantageous to me.

I was intimidated by AlphaGo’s reading becoming more accurate approaching to the end. I heard that others questioned why I did not play a ko in the top right. However, it is meaningless. I did not need to play a ko, and AlphaGo’s ko play is at a professional level, as seen in the match with Fan Hui 2 dan. People who are not in the ring do not know what it is like in the ring.