I wonder if this also works the other way around with good moves instead of just avoiding blunders.
A parallel in business: we spend so much time thinking about hiring "A players" and "10x-ers". But could refocusing on better processes, environment, and goal-setting (reducing the complexity of the position) be just as effective for increasing performance?
tl;dr We find strong evidence that in our domain, features describing the inherent difficulty of an instance are significantly more powerful than features based on skill or time.
I would to see more how the study was done because i highly doubt this could be possible.
It can be the case that in high ranked games the oponent will put you in harder spots, and errors will comes.
But by definition, better players take better decisions Ev average.
An interesting study will be a list of leaks the population usually have.
For exemple in pkker before solvers, people with a very strong hand on flop, lets say straight draw+ flush draw, when the board turn bad for them, they are way more likely to call a bet on river, because they hand was so strong on flop.
Solver will show is a bad call because you block possible bluffs opponent could have (flush and straight draws) so his value range is bigger.
Regardless, this doesn't seem that surprising to me. Highly skilled players have developed a set of tools, techniques, and analysis that they are very familiar at applying. If a game enters a particularly strange but still complex position, one that would never really arise under usual high-level play, it is plausible to imagine unexpected errors may occur from time to time, as the standard high-level heuristics may not work exactly the same. Especially if the higher-level player is not being very careful.
The lower-level player, not having those heuristics, must look at the situation, like they do all positions, with a fresher perspective and far less expectations. They won't make the mistake that can come from misapplying the heuristics and tools of higher-level play, because they don't even have those heuristics.
Of course, these are specific, uncommon situations. In general, the advanced player will almost always make much better moves than the less-skilled player.
Note that this is only true when expected value lines up exactly with "increases probability of winning". Lots of value calculations don't, and so better play can look strange in some situations.
Back when I was a middling chess player in High School, I'd pretty much always play King's Gambit as white when it was offered, especially against stronger players. I knew that I didn't study openings as much as other players, so I wound up in a place where I at least had as good opening book knowledge. Plus the opening is high variance, so it gave better opponents more chances to screw up and let me in the game. That said, the consensus high-level opinion on King's Gambit is that white does not get sufficient compensation for the pawn.
Or perhaps and even better example is AlphaGo Zero. When this engine is winning a Go game as it gets into endgame, it will play lines that confuse the professionals as locally sub-optimal. The pros later figured out that these moves would give up points in exchange for removing lines of play that are threatening and uncertain: instead of winning by 2.5 points with a small opportunity for the opponent to come back, AlphaGo Zero would win by 1.5 or 0.5 points without yielding any counter-play.
In the case of alphago, all depends how ev is calculed, % winning or points.
A critical factor that the study did not consider at all was your opponent's remaining time. The stronger player is generally going to be the player that has more time left, often much more time. If you have 20 seconds and your opponent has 2 seconds left the easiest way to wrap up the game is to just make a move, any move. This means the quality of move is going to go down in a vacuum. By contrast you won't find this situation as frequently from the weaker player since they'll rarely be meaningfully up on time.
Another related pattern is that in a dead drawn time scramble a weaker player is going to be more likely to make a blunder, such as hanging a piece. And not exploiting that move (such as by taking the piece) would itself be a blunder. But in a time scramble with just 2 pieces vs 2 pieces you're often just making semi-random moves as quickly as possible - meaning you will miss the hanging piece. Again for similar reasons this is not an issue you'll find as commonly from the perspective of the weaker player both because they'll less often be substantially up on time and because the stronger player is less likely to randomly blunder, meaning just making a random move is itself less likely to be a blunder.
One theory could be that stronger players are going for a win which requires more risk while weaker players are happy to play a non-aggressive move looking for a draw.
Unfortunately the article didn't state if most blunders come from being ahead or behind in material.
The pro may calculate a huge line that requires breaking a simple rule, and in the end that may come back to bite them. Where me, all I see is "hey don't leave the knight on the edge like that."
He said that he was commonly surprised when he'd make a move that would be immediately seen by his peers as aggressive, or strong, and cause them to back off or fold, while with us, it just went right over our heads and we'd miss it entirely...
Seems like lower-skilled players could simply not see some of the complexity that confounds a higher skill player, and an even higher skill player would handle. A sort of local minima anomaly for skill.
Or, maybe like tho old saying: "Fools rush in where angels fear to tread".
The biggest challenge for me when I play less-skilled players is to maintain a solid showdown game — it just gets boring compared to high-level play.
Anyway I'm not sure they could control for the skill of the players in both sets, because their dataset is probably missing amateur-vs-skilled data, which probably renders most of their skill-based correlations incomplete, as we don't know if they correlate to the skill of the player making the mistake or their opponent.
My experience has been that, in everything with a competitive aspect, there is a phenomenon where suboptimal choices become optimal because they are unexpected.
Chess, war, video games, sports, everything. As you point out, in the long run, the better player comes out ahead. That's what "being better" means. But the long run isn't always what counts. Sometimes two competitors are going to meet exactly once or the situation is going to be "winner takes all".
Can u please explain what are "solvers"?! I used to be involved in online poker software but I am out of date by about 10 years.
Equilibrium it means both of the players cant deviate from the strategy without loosing.
It is 33% rock, 33%paper 33% scissors.
Also important point to note is that most chess masters avoid reaching this complex position and that itself is an important skill. The best way to solve a problem is to avoid it from happening.
GMs like Garry Kasparov would deliberately go into complex positions to confuse their opponents.
Silman has spoken / written about the little-discussed but non-negligible role that chance / stochastic processes have in the outcome of chess games. In one of his books [I think the recent edition of 'Reassess You Chess'], he ballparks chance at something like 10% of the total factors influencing outcome.
If I play someone much lower-rated than me, it's hard to care much about the game. I will play careless aggressive moves, make reckless sacrifices, thinking anything will be good enough.
They will be playing a much higher-rated person. Winning will mean a lot to them, they'll try hard, focus intently, make the most of resources etc.
Because of this, I've often had the impression that higher-rated people are easier to beat than lower!
Then when you get in a very easily won position, it's really hard to keep focus, you just think it's already won, are already celebrating in your mind. But in chess, one slip is often fatal, no matter how winning you are. Or there are stalemate tricks, and the win is thrown away. And the more you're winning, the more paths to victory to select from, and the less you care to think about it. You impatiently wonder why the other guy hasn't resigned already. Thus the saying "There's nothing harder to win than a won game".
When you are losing, you focus, use every resource... Survival mode kicks in.
Also, they used endgames with IIRC < 7 pieces, so again, some derivative work might use middlegame positions and use engine analysis as an oracle, similar to Regan's work (http://www.buffalo.edu/news/experts/ken-regan-faculty-expert...).
"According to my experience in chess, the most difficult in chess? To see moves with knight back." @5:34 --Ivanchuk
The higher the skill, the higher are chances of blundering probably because:
1. Higher complexity
2. Very high likelihood of being punished for it. At lower elo, your opponent probably didn’t realize the blunder either.
> Quick decisions are more likely to lead to a blunder, but after about 10 seconds or so the likelihood of a blunder flattens out
> More difficult positions are more likely to lead to a blunder. And skill levels have a big impact in reducing the likelihood of a blunder. In general, better players make better decisions.
> The bottom line is that the difficulty of the decision is the most important factor in determining whether a player makes a mistake. In other words, examining the complexity of the board position is a much better predictor of whether a player is likely to blunder than his or her skill level or the amount of time left in the game.
They have an new definition of blunder - "a player has committed an error if their move worsens the mini-max value from their perspective. That is, the player had a forced win before making their move but now they don’t; or the player had a forced draw before making their move but now they don’t. ...we will refer to such an instance as a blunder." .. "Since we are interested in studying errors, we exclude all instances in which the player to move is in a theoretically losing position — where the opponent has a direct path to checkmate — because there are no blunders in losing positions (the minimax value of the position is already as bad as possible for the player to
"Our data comes from two large databases of recorded chess games. The first is a corpus of approximately 200 million games from the Free Internet Chess Server (FICS), where amateurs play each other on-line. The second is a corpus of approximately 1 million games played in international tournaments by the strongest players in the world. ... we focus on this large subset of the FICS data consisting exclusively of games with 3 minutes allocated to each side."
I've played 10,000+ games on FICS, so I have some idea how it works. Players have a standard, blitz and lightning rating, all separate. 15 0 and slower counts as 'standard', anything faster down to 3 0 is blitz, anything faster than 3 0 is lightning.  3 0 is a different world to 14 0, so treating those ratings as the same is already misleading - I often played 5 14 (i.e. 5 minutes on your clock to start, plus 14 seconds added on after each move), a bit faster than 5 15, which is counted for rating purposes as the same as 15 0. (It assumes a game goes for 40 moves, so 5 minutes + 15 seconds x 40 moves = 15 minutes.) So 5 14 is the slowest blitz speed. If I played someone rated the same as me whose rating mainly came from 3 0 games, they would be much stronger than me at 5 14. (Usually, on FICS, the faster the time control, the higher the rating. And obviously the more time you have, the better moves you make.) The point being - someone's blitz rating didnt mean they got it playing at 3 0. It's not their 3 0 rating.
Also, FICS doesn't use Elo. (It uses the Glicko rating system) The paper's authors seem unaware of that, or maybe I missed the part where they explained how they converted between FICS and Elo. As far as I know, it's not possible. There's not a linear relationship, or any simple conversion formula. From memory, lower rated FICS players have higher Elo, higher rated FICS players (over 2200) have lower Elo etc. But chess websites have a variety of rating systems, none of them compatible, commensurable or equivalent.
Sadly, I kind of lost interest there. I meant to study the paper more thoroughly. But already that rating confusion seems a huge 'blunder'.
 https://www.freechess.org/Help/HelpFiles/blitz.html https://www.freechess.org/Help/HelpFiles/standard.html