# You can’t calculate what you can’t see

I was playing online blitz early in the morning this week when my opponent fell into a well known mating trap on move 8.  The mating pattern is very pretty and always satisfying but it also occurred to me that it appeared to be one of those positions that everyone seems to fall into.  Bemused at why this would be the case I decided to look at some statistics and noticed that despite being a relatively rare line, every time I had had the position my opponent had walked into the trap.  I’ve talked about the difference between amateur and professional players before and this sequence is another lovely example.

The line in question stems from the Chigorin Defence of the Queens Gambit Declined.  After 7…Nxe5 it first appears that black is losing a knight.  However, it doesn’t take too much calculation to spot the checkmate threat on d1 should white decide to snaffle the knight on e5.

Indeed after white allows 7…Nxe5, black has equalised and discretion is the better part of valour for white with recommended moves such as Be2 or Nbd2.  However, in the four times I have had this position arise in my games, all four times I have delivered checkmate on d1 on move 8.  Now we can argue that these games are online and amongst amateur players but I do find it fascinating the confidence with which the black knight is snaffled on e5.  Sometimes the white player plays the mistake instantly, sometimes they think for a long while and still play the move. Why is this?

It is a common mantra amongst chess professionals and coaches that good players know when to start burning time in complex calculation.  Knowing when to invest time is a key skill. However, as well as knowing when to spend time calculating you also have to know what to calculate.  If you don’t see a threat or are blind to its existence then you will not calculate and obviously miss the risk resulting in losing to checkmate on move 8. The position in our line we are analysing, I believe, is a very good example of a position that the amateur mind struggles with.  There are a number of factors at play in the position, one or all of which could contribute to this very common mistake.  Lets list them out:

• A queen less early middle game – Only two pieces are developed by either side and the queens have left the board.  Why would white necessarily be on the look out for mating threats against his own king?  Indeed, he or she has to calculate the knight capture doesn’t lose material (and it doesn’t) but an actual mate threat is not on whites radar;
• The threat only arises from a vacated square – The checkmate is only possible by white releasing the power of the bishop onto d1 by vacating f3. Threats occurring by vacating squares are intrinsically harder to visualise when calculating;
• The knight capture wins material – Whats not to like about winning material?! Greed is a powerful bias;
• Its easy for white to believe black blundered – Until a move earlier the knight on f3 was pinned.  Following the exchange of queens this is no longer the case but it is easy to see how white would think black had miscalculated and blundered by grabbing the e5 pawn by telling themselves that black thought the f3 knight was pinned;
• The capture on e5 creates nice threats on blacks king – As well as all of the above points, the white pieces start to build a lovely threat on f7 against blacks king.  Its easy to see how white could spend time calculating future threats and attacking options while simultaneously missing threats against his own king.

Having read the above list now lets look at the position side by side with the board flipped. Try looking at each board position and then running through the kind of thought process that white would be walking through.  I don’t know about you, but I actually think the threat is harder to see from the white side of the board because the position for white seems so appealing.

The same position from both white and blacks perspective.  Hard to believe that a mate in 1 threat exists and how the board can appear  so different from either side.

To be fair, I don’t know how many of the above factors contribute to the blunder 8. Nxe5 but it is highly likely some of them play a significant role (NB – Not a lot of people know that I am professionally trained in the analysis and evaluation of human error in complex environments.  A story for another time…).

Here we have a tempting position for white with many positive features such as material gain and kingside attacks combining with a very subtle, hard to see, totally unexpected terminal threat. A nasty combination for the amateur chess player to comprehend which seems to be the chess equivalent of all that glitters is not gold and bring me nicely to the title of this blog post.

## You can’t calculate what you can’t see.

In our example, the amateur white player can calculate for as long as he or she likes but if they do not recognise the danger of checkmate then they will simply run analysis on the safety of their developed pieces and the opportunities for future attacks. Many stronger rated players could often laugh and scoff at such a blunder as 8.Nxe5 but I believe this would be unfair.  Human chess players (amateur and professional alike) are not computers. They do not calculate everything.  They only choose to calculate what stories they tell themselves.

“She’s just blundered that knight.  Surely she cannot take my pawn on e5?”

“If I take it then f7 looks weak”

“Queens are off.  There are no real threats at the moment.  I don’t see how he is gaining the piece back it must be a blunder”

“My f3 knight is no longer pinned!”

If your internal dialogue is spinning stories with a different narrative to the reality of the position on the board then the amateur player is in trouble.   In my games 100% of amateur players blundered and walked into checkmate on move 8.  Of the 9 Master Games in the database I looked at 0% of professionals did. Indeed the skill set  to remain completely objective when looking at any position is likely one of the key defining characteristics of weak vs. strong players.

I just loved this example as it seems to fall into that rare category of positions that really seems to befuddle the amateur mind.

Until next time…

Jon Fisher

Jon is the Editor of The Bristol Chess Times and Publicity and Recruitment Officer for The Bristol & District Chess League. He plays for Horfield Chess Club and has been known to play 1. b3 on occasion.

## One thought on “You can’t calculate what you can’t see”

1. Mick says:

Very interesting article. I’d suggest though that there are additional factors.

The failure of players in published games to fall for the NxN blunder may be down to the fact that they are still in theory and so the position (and blunder!) are known to them – they see it because it’s been shown to them.

Also in blitz, players rely on instinct much more than calculation – you have brilliantly set out those instincts – so the lack of time plays a significant part in the self inflicted demise.

Professional players blunder too, and as a rank amateur myself it is always heartening to see (very) strong players do this – especially in blitz games or otherwise in time trouble. This isn’t out of schadenfreude, rather it exposes how difficult chess is for all of us.