A Peculiar Type of Blunder: Confusion
Yesterday I was trying to solve this chess puzzle and I got it wrong in a way that I found really interesting and significant. In terms of "brute best moves" I analysed most lines well enough, even reached the correct evaluation of the position, yet I simply made the wrong move. How did that happen? I'll tell you, but be warned, it's not going to make any sense.
Here's the position with black to play. Try to analyze it yourself before moving on.
(Hint: The server that fed me the problem occasionally asks you to find a draw, so it's not necessarily a win or mate).
And here's how I got incredibly confused and played the wrong move even if I had worked out the crucial things right:
There are two main candidates in the position: Ne4 and Na4. I calculated (correctly) that white can force a draw after 1...Ne4 2.Ng5+ Nxg5 3.Qd8 Ne4 4.Qh4+. I thought I got this variation settled and switched to analyzing Na4 deeply. At this point I was still looking for a win and everything was going well until I finally saw 1...Na4 2.a3, after which I simply couldn't force a thing, the discovered checks with my queen wouldn't work anymore as it was under attack, and white had enough tempi to cover every weakness. That made me realize I was looking for a draw in this position, which is the correct verdict, and then things got worse.
I couldn't even find a forced draw after 1...Na4 2.Qd8 Nc3+ 3.Ke1 Ne4+ 4.Nd2 and the knight is protected (which is again, correct analysis). Then something incredible happened. I returned to 1...Ne4, confirmed that white could force a draw and I had no win there, and went back to try to force a draw myself with 1...Na4. In the end, I thought, "I'm absolutely certain that 1...Ne4 is a forced draw," so I eliminated it, and played 1...Na4 with the idea that it was the only option left where I could perhaps possibly force a draw but simply couldn't find it in my analysis (because I wasn't 100% sure).
Let me try again to make clear how crazy that line of reasoning was: I discarded Ne4 because white could force a draw, then tried to force a draw myself with Na4, couldn't pull that off, returned to Ne4, confirmed my judgement, and went back again to Na4, couldn't pull a draw again, but played Na4 anyway hoping I had somehow missed something. I know it doesn't make sense at all. That is because it's nonsense. That is how confused I got. I think it was partly because in one variation it was white who forced a draw (with the unconscious implication that I was pressing for a win but failing) and in the other, I was the one trying to force a draw (which would be, in that case, an accomplishment).
So there's this peculiar type of blunder in chess. It's not missing a candidate move (oh white had a check!), it's not laziness (meh, this has to be winning, how bad could it be anyway), it's not having an illusion (you see a pin deep in your tree of analysis but it's actually not there), it's not even a misjudgement (you evaluate the final position of your analysis as winning but it's actually not). It's just simple confusion.