GPT4 can play chess

July 29, 2023

How general are Large Language Model (LLMs) chatbots?

If you're interested in how AI will play out over the next few years, you might care how much "general" intelligence is embedded in these systems. Do they just predict text? Or can they learn to do other interesting things?

Twice today I saw a experts use chess as an example to show that they aren't very general.

In an interview a few weeks ago with Ezra Klein, Demis Hassabis (CEO and co-founder of DeepMind) said:

So if you challenge one of these chat bots to a game, you want to play a game of chess or a game of Go against it, they’re actually all pretty bad at it currently, which is one of the tests I give these chat bots is, can they play a good game and hold the board state in mind? And they can’t really at the moment. They’re not very good.

In a roundtable with Eliezer Yudkowsky and Scott Aaronson, Gary Marcus said:

I would say that the core of artificial general intelligence is the ability to flexibly deal with new problems that you haven’t seen before. The current systems can do that a little bit, but not very well. My typical example of this now is GPT-4. It is exposed to the game of chess, sees lots of games of chess, sees the rules of chess but it never actually figure out the rules of chess. They often make illegal moves and so forth. So it’s in no way a general intelligence that can just pick up new things.


I mean, to take the example I just gave you a minute ago, it never learns to play chess even with a huge amount of data. It will play a little bit of chess; it will memorize the openings and be okay for the first 15 moves. But, it gets far enough away from what it’s trained on, and it falls apart.

But they can play chess!

A couple months ago I saw some tweets about how GPT3.5 and GPT4 can play chess if you give it very specialized prompts. (That same account has some other interesting examples showing a "logic core" in GPT.)

That made me curious to try more "normal" prompts, and I found that if you prompt it like this:

Let's play chess. I'll start.

  1. e4

... and proceed with standard PGN notation, GPT4 makes reasonable, legal moves, even long after the opening.


(I don't know why GPT4 is refusing to increment the move numbers with me. When I tried this a couple months ago its move numbers made sense. You'll see in the transcript I got one move number wrong myself.)

I don't know what Demis considers a "good game", but it seems pretty clear to me that GPT4 is able to "hold the board state in mind".

Here's the final position in the game I just played (GPT4 won):


You can see the full transcript here.

To see the full game played out, go to a analysis board and paste in the game's PGN notation:

1. e4 e5 2. d4 exd4 3. Qxd4 Nc6 4. Qd1 Nf6 5. Bc4 Bc5 6. b4 Bxb4+ 7. c3 Ba5 8. Nf3 O-O 9. O-O Nxe4 10. Re1 Nf6 11. Qb3 d5 12. Rd1 dxc4 13. Rxd8 cxb3 14. Rxf8+ Kxf8 15. axb3 Bg4 16. Ba3+ Kg8 17. Nbd2 Re8 18. Re1 Rxe1+ 19. Nxe1 Bxc3 20. f3 Bxd2 21. fxg4 Bxe1 22. Kf1 Bb4 23. Bxb4 Nxb4 24. Ke2 c5 25. g5 Ne4 26. h4 b5 27. Ke3 Nd6 28. g4 a5 29. h5 a4 30. bxa4 bxa4 31. h6 gxh6 32. gxh6 a3 33. Kf4 a2 34. Ke3 a1=Q 35. Kf4 Qf6+ 36. Ke3 Nd5+ 37. Kd2 Qf2+ 38. Kd3 c4#

Aside from the move numbers, there's one way in which this record of the game differs from our transcript: On move 17, I said "Nd2", which is an incorrect thing to write, since there are two knights that could move to d2. But GPT4 just went with it, and seems to have correctly figured out which one I meant.

Could this game be memorized?

I can't really prove to you that this game isn't in GPT4's training data, but it seems exceedingly unlikely. I made some intentionally weird moves just to try to get out of any common sequence pretty early.

Is GPT4 good at chess?

This isn't a particularly good chess game, though it's me rather than GPT4 who didn't play very well. I blundered a piece on move 12, and (as mentioned) made a few other intentionally not-good moves.

I don't really know how good GPT4 is at chess. If I can get API access, I'd love to try making a chess bot that could play online.

Why can GPT4 play chess?

I don't work in AI these days, but I'd guess that: GPT4 is trained to predict the text in its training data, and presumably there are a lot of chess games out there on the internet for it to read. By learning the rules of chess and some ability to reason about the board state and good moves, it does a better job predicting those games.

Did I cherry-pick this example? Is this behavior reliable?

First, I even one example like this shows that GPT4 is able to hold the board state in mind. If I'd had to play 100 games where forgot the board position, even one where it tracks the board and plays pretty well is interesting.

But no, I didn't cherry-pick the example. I played a little bit in this format a couple months ago (and I don't think GPT4 made any illegal moves), and then today after seeing these comments that chat bots can't play chess, I tried one and only one game. That's this one. I didn't play any other game for this post, and certainly not any where it made illegal moves and I gave up.

I tried this a couple other times two months ago, but I don't have great data on how often GPT4 is able to complete a game this way.

But it does make illegal moves for some prompts...

Using prompts like the one above seems to work well, but it's true at GPT4 can quickly go off the rails with other prompts.

Here's an example where I asked it to explain its moves, and its 4th move was illegal. That's a big contrast with the above 38-move game where it plays legally the whole time, and wins!


Also here's a chat with the same initial few moves where it plays legally.