[fasthands9]

I know very little about chess.

Do computers play like top humans? Or different stylistically?

ie - if you were a top player and looking at the moves of an opponent, could you discern if the style was more similar to a top rated human or a top rated computer?

[CSMastermind]

There are "computer moves" which stand out vs human players. These normally show up in lines where there are many options of roughly equal value and the computer picks a move that is infinitesimally better but out of 'theme' with the position.

They can also show up when for instance there are multiple checkmates in a position. The computer will choose the one requiring the least number of moves even if it requires deep calculation and perfect play. Humans will just trade off material and go for an easy win.

Now that chess engines have started to use neural networks in move selection the amount of "computer moves" has decreased noticeably.

> if you were a top player and looking at the moves of an opponent, could you discern if the style was more similar to a top rated human or a top rated computer?

With a large enough sample size I believe that top players would be able to tell the difference. But that sample size is much larger than a single game or likely even the ~10 games being played in a tournament.

Edit:

Oh I should also mention that in the context of cheating with computers there are more signals to look at than the moves themselves. Time management is normally a huge giveaway for cheating. In online chess this normally manifests itself as players using the exact same amount of time for each move in spite of the positions being very different in terms of complexity.

In the match being talked about above Hans, the challenger, used a suspicious amount of time during the opening sequence. He played the opening moves in around 10 minutes which is weird because if he had memorized the lines he would have played them much faster. If he didn't memorize the lines then it would have taken him much more than 10 minutes to calculate it all.

[stouset]

> There are "computer moves" which stand out vs human players. These normally show up in lines where there are many options of roughly equal value and the computer picks a move that is infinitesimally better but out of 'theme' with the position.

To elaborate on this, humans use pattern recognition to identify themes within a position. This is a shortcut that prevents needing to mentally brute-force your way down an enormous tree of possible positions. Elite chess-playing humans are very good at this, but are still very good at spotting potentially non-thematic (perhaps "surprising") moves that offer some quantifiable advantage.

Computers operate very differently from humans. They rigorously evaluate positions to absurd depths. They can examine lines further than 30 moves deep without too much time. Often the moves they come up align with the thematic ideas that humans have (after all, there's a reason why humans have identified these patterns). But at the end of the day, the computer isn't playing thematically. It only cares that the position at the end of best-play by both sides has the score most in its favor.

This leads to computers playing moves that humans would only come up with exceedingly rarely. And if a human came up with that move, there would generally be some clearly-identifiable reward that humans can pick up on several moves later. When a human player plays computer moves, those noticeable rewards are often missing. The cheating human makes a puzzling move, play continues, and many moves later their opponent is worse off. But even after serious analysis it's not entirely clear how that original move brought about this advantageous position.

Of course maybe the human in question really wasn't cheating and stumbled into a brilliancy. Perhaps it's even one they didn't even truly understand the ramifications of when they played it! But when a human makes several of those types of moves in a single game, or even across a single tournament, it brings about extreme suspicion.

[aoeusnth1]

If this interests anyone reading this, check out this Daniel Naroditsky video where he analyzes positions with some astounding engine moves which are very difficult for humans to see, but do have logical reasons for why they work: https://youtu.be/GdaU7wpOArs

[threatofrain]

If there is too little communication between you and behind-the-scenes cheating operator, you run the risk of choosing a move which requires perfect play for a long sequence, otherwise it would give away that you didn't understand the move.

[Andrew_nenakhov]

This is a rather poor example. If there are multiple checkmates, humans are usually much more likely to see ones that require the least number of moves. Anyway if there are multiple checkmates, the game is irrecoverably lost by another player and it is easy to see on the board.

[myownpetard]

It's more complex than this.

The situation would be more like, there is a forced checkmate in 12 but it involves navigating a sharp position that is complex and any miscalculation could equalize the position.

On the other hand, you can simply exchange queens and rooks and have a clear winning endgame, but it will only result in a checkmate in 20 moves.

Almost any human would opt for the latter to avoid the risk. From the computer's perspective, there is no risk.

[Andrew_nenakhov]

I tend to analyse my games after playing them, and I must say that NOT ONCE in a few hundred of games played at my level (~2500+ on lichess rapid) I have seen a forced mate in 10+ moves other than in end-game when there are very few pieces on the board left. And when you see such long checkmate, usually it doesn't really matter, because by then all is already clear on the board.

So no, I stand by my point that a specific choice of one of multiple possible checkmates is quite a poor indicator of using a computer to calculate moves.

[myownpetard]

That's surprising to me especially for rapid but you're better than me (2000 lichess). Under time pressure, if I have a passed a or h pawn and can simply trade down and promote I will opt to do that rather than try to calculate a deep mating combination.

> other than in end-game

This is frequently where such scenarios occur. Many end games are difficult for humans to play with absolute precision, even seemingly simple ones like knight and bishop vs. king. But when there are fewer pieces on the board is exactly when computers are able to perform incredibly deep calculations.

A good example is the notorious 30 move forced mate that Caruana "missed" in game 6 of his world championship match with Magnus, which occurred with only 3 pieces and 3 pawns left on the board.

[Andrew_nenakhov]

To be honest, I'm lazy and rarely calculate more than a couple of turns: I just have a mental picture of what I want to achieve and seek ways to get there.

However, I do look up a post-game analysis, and if there are some mid-game deep checkmates, they show up in it, and it is extremely rare. The example you cite about Caruana/Carlsen game actually quite falls into the category of what I referred to as 'endgame mates' - and looking at it with a potentially cheating player in mind, such cases are rather irrelevant: a cheater will win a game or arrive to an overwhelmingly better position in the endgame so such extreme measures with 30+ precise move checkmates will not be necessary.

[underdeserver]

This is false. If there's a longer mate where every move from your opponent is forced (that is, only one more is legal or doesn't immediately lose) a human player will play that, as opposed to a shorter mate, in say 5 moves, where you have all sorts of different cases to calculate depending on what your opponent plays.

[Andrew_nenakhov]

You should be more careful with such statements. Boldly claiming that something is 'false' and backing it up with a rather vague hypotheticals does not make your statement look good, considering that said hypotheticals are not supported by my own chess playing experience. Of course, I don't claim to be a really strong player or something, and my lichess rapid rating is only ~2580, so maybe your expertize in these matters exceeds mine.

[georgiecasey]

That's a serious lichess rapid rating. Are you a titled player?

[Andrew_nenakhov]

I don't think so. I only started playing online a couple of years ago to relax, but ~30 years ago I used to go to chess school for a few years and had a First class sportsman degree [0], and even barely qualified for a Candidate for Master of Sport after a couple of local tournaments, but it wasn't awarded to me because I simply stopped appearing: it coincided with me losing interest in chess as time limits on that level grew to ~2+ hours and that was far too much for my jumpy ass. So I don't think that First class title is still active, as even the country that awarded it to me - USSR - doesn't exist any more.

[0]: https://en.wikipedia.org/wiki/Unified_Sports_Classification_...

[grumpopotamus]

The top chess engines are now much much stronger than humans, and they will find some moves that grandmasters are unlikely to even consider. One recent example was Kf8 in the recent Patrycja Waszczuk cheating scandal: https://www.chess.com/news/view/patrycja-waszczuk-cheating-2.... I watched Hikaru Nakamura analyze the game on stream and he burst out laughing when he saw the infamous Kf8 move, since it was such a bizarre move for a human to play.

[andy81]

Link to stream highlights - https://www.youtube.com/watch?v=3BgVe_Jp4Ys

That Kf8 really is the move of somebody living in another universe.

[faeriechangling]

I can't find a citation but I recall that computers agreed with the moves of grandmasters from the pre-computer era about 60% of the time.

Generally, the biggest heuristic for identifying cheating is identifying somebodies moves share statistical similarity to the top moves of common engines (Especially stockfish). This doesn't really work after a single game, but anybody playing the top move of stockfish 90% of the time over 100 games is a cheater. Nobody that isn't cheating can do that. Cheaters are savvy though, they will notice in a position there are maybe 5 decent moves they can choose from, so for just that position they will choose stockfish's 5th choice. Or maybe they'll only check the engine at the most critical moments of the game and turn the engine off and play normally afterwards. Notice that the person being debated in this article is somebody with a history of cheating, the evidence they cheated in this specific game is likely not as good as the evidence they are just generally a cheater.

On top of this more empirical analysis, there's more subjective analysis. Humans tend to try to simplify games when they're ahead to reduce computational complexity, but computers don't do this as it's not a good strategy for a computer. Humans will tend to follow a narrative and follow a general idea throughout a game with ideas they calculated earlier in the game or in their preparation, whereas computers don't care about narratives and will completely switch plans on a dime. In the endgame the computer starts having a LOT of winning moves that it hasn't calculated to the end and can start making very offbeat choices, whereas humans tend to use a set of rote memorised strategies that are known wins. Again though, a skilled cheater realises all this and will choose weaker more human-like moves that are probably the engines 2nd or 3rd choice.

There's also metadata. Cheaters usually take a few seconds to think about a move that a human would make instantly (this came up in the article where it took the cheater 20 seconds to make their first move), they probably exhibit different browser/app interaction habits. Humans have all sorts of particularities about UI interaction and time management. A lot of people play blitz and bullet chess because cheaters struggle to cheat convincingly under time pressure.

[okamiueru]

> 20 seconds to make their first move

At this level, players know all opening lines to some depth. The first move? I don't see how 20 seconds indicate anything other than a passage of time.

[faeriechangling]

Well in this case it did actually indicate something other than the passage of time, it indicates the player was using a shoe operated cheating device an remarked on how he would normally move more quickly.

Maybe I overemphasized the first move because it was emphasized in the article, in general cheaters use their clock in weird ways throughout the game since for them pretty much any move is similarly complex. In this case the shoe operating cheating device raised the minimum time to make a move, which is a characteristic common to many forms of cheating.

[bjourne]

Yes, you could very easily do that. However, the theory is that cheaters would let the engine decide only 3-4 critical moves during a game and that would be enough to turn the tide in their favor. In chess small advantages compounds so this computer help would be enough for grand masters to beat the world champion. A cheater that understands cheating countermeasures could easily fly under the radar that way.

[sgjohnson]

The problem with this approach is that you'd still need to be able to correctly identify those critical moments in the game, and a single move won't help you. You need the entire line.

Which would still require a considerable skill. If you can't figure out why a single move is brilliant, you won't be able to find the entire line.

If stockfish tells you the entire line, and the opponent plays something that wasn't included in stockfish's line (because it's worse), you're also going to be at a loss.

[ciphol]

If you're playing Magnus Carlsen, you're probably pretty skilled to begin with.

[tstrimple]

The best cheaters are also highly skilled. This is true in online competitive games as well. Very rarely do these folks just leave cheats on all the time. That's blatant and easy to ban. But toggling it on at critical moments will give you those "clutch" wins which genuinely happen sometimes, but makes them much more reliable.

[seanhunter]

There are certain moves that players will absolutely call "engine moves". These are usually moves with no discernable purpose (even when calculating deeply) that later on turn out to have been crucial dispite the fact that they don't seem to progress any conventional goal or deal with any current concrete threat. If you analyse a game with Stockfish you'll often see it suggest (say) a calm-looking king move that no human would ever play in the middle of a massive attack but that turns out to resolve some deep positional issue later on.

The clearest example in modern play is a4 and h4 as white (eg early h4 vs the King's Indian Defense) or a5/h5 as black. These are now frequently played in various positions because since they were discovered a few years back by alphazero, they have been extensively examined and found to be good, but prior to that, no strong human would play them.

[camjohnson26]

If every move was an engine it would be suspicious, but it would be easy to just use the engine a few times at important moments in the game to get a huge advantage, and it would be very difficult to detect. The top player normally know the best few moves on the board and choose between them based on long term strategy.

[ummonk]

Top humans tend to pick a slightly weaker move than computers every few moves. By letting the computer veto their chosen move sometimes but not all the time (and only doing so when the computer's chosen move was one they were strongly considering), they can have stronger performance without anyone catching on.

[ken47]

The top chess engine was ELO rated at 3546 in 2021. The top rated player ever was Magnus at 2882. To put that ELO difference in context, even if Magnus gets the first move, the chess engine is expected to win 0.979934616 of the time. Within that gap, there are many moves that can be played that are superior to human moves by varying degrees.

It would be very hard to detect a sophisticated cheater solely by examining their moves in a vacuum. They could pick moves that appear to be "human" e.g. moves that appear to be chosen based on the common heuristics that strong human players tend to rely upon, rather than moves based on very deep brute force calculations, where we could never match the strongest chess engines.

The giveaway is usually in the time required for each move. Humans will tend to spend varying amounts of time on each move, with significantly more time spent at critical moments in a game. A computer will pretty much spend the same amount of time for each move. But even here, a sophisticated cheater could disguise this side effect by only using computer assistance at critical moments.

[1] https://wismuth.com/elo/calculator.html#rating1=3546&rating2...

[thret]

Agadmator covered this game and explains a disgusting computer line quite well. Note that under time pressure, a human can only calculate so many lines. They will immediately see a range of possible good lines, explore them to some depth and choose the best looking one. This engine line takes a bad looking path which comes good only after 19 moves.

https://www.youtube.com/watch?v=64o62MrhvXc&t=1400s

[colechristensen]

There are some grandmaster chess streamers who play random people on the internet and pick up rather quickly when they are playing against a chess engine instead of a person.

In a nutshell, computers do some things that are very unlikely for humans to do. A lot of the play is similar, but some things are outliers and high level chess players will notice the unusual style and high accuracy moves of a person assisted by a computer.

[hocuspocus]

In the moment I doubt a top GM would notice. Everyone is preparing using state-of-the-art chess engines and taking inspiration, even from moves that would have been considered crazy a decade ago.

After the fact, it'd probably be more obvious. Human players will typically avoid unnatural moves that require long sequences of perfect play before they pay off.

But top players are also the best qualified at cheating in a way that wouldn't raise suspicion. Many games are lost or drawn because of small mistakes or inaccuracies during the endgame. And playing a perfect endgame is not implausible at this level.