 Dear Fellow Scholars, this is two-minute papers with Karo Zsolnai-Fehir. This work doesn't have a ton of viewable footage, but I think it is an absolutely amazing piece of craftsmanship. So in the first half of this video, we'll roll some footage from earlier episodes, and in the second half, you'll see the new stuff. In this series, we often talk about reinforcement learning, which is a learning technique where an agent chooses an optimal series of actions in an environment to maximize the score. Learning computer games is a good example of a clearly defined score that is to be maximized. As long as we can say that the higher the score, the better the learning. The concept will work for helicopter control choosing the best spot for Wi-Fi connectivity or a large variety of different tasks. However, what about environments where multiple agents or players are present? Not all games are single-player focused, and not all helicopters have to fly alone. So what about that? To deal with cases like this, scientists at OpenAI and the University of Oxford came up with a work by the name Learning with Opponent Learning Awareness, L-O-L-A in short, or Lola. I have to say that the naming game at OpenAI has been quite strong lately. This is about multiplayer reinforcement learning, if you will. This new agent does not only care about maximizing its own score, but also inserts a new term into the equation, which is about anticipating the actions of other players in the environment. It is not only possible to do this, but they also show that it can be done in an effective way, and the best part is that it also gives rise to classical strategies that game theory practitioners will immediately recognize. For instance, it can learn Tit4Tet, which is a strategy that mirrors the other player's actions. This means that if the other player is cooperative, it will remain cooperative. And if it gets screwed over, it will also try to screw others over. You'll see in a moment why this is a big deal. The Prisoner's Delama is a game where two criminals are caught and are independently interrogated and have to choose whether they snitch on the other one or not. If anyone snitches out, there will be hell to pay for the other one. If they both affect, they both serve a fair amount of time in prison. The score to be minimized is therefore this time spent in prison. And this strategy is something that we call the Nash equilibrium. In other words, this is the best set of actions if we consider the options of the other actor as well, and expect that they do the same for us. The optimal solution of this game is when both criminals remain silent. And now, the first cool result is that if we run the Prisoner's Delama with two of these new Lola agents, they quickly find the Nash equilibrium. This is great. But wait, we have talked about this Tit4Tet thing. So what's the big deal with that? There is an iterated version of the Prisoner's Delama game where the snitching or cooperating game is replayed many, many times. It is an ideal benchmark because an advanced agent would know that we cooperated the last time, so it is likely that we can park her up this time around too. And now comes the even cooler thing. This is where the Tit4Tet strategy emerges. These Lola agents know that if the previous time they cooperated, they will immediately give each other another chance and again get away with the least amount of prison time. As you can see here, the results vastly outperform other naive agents and from the scores, it seems that previous techniques enter a snitching revenge war against each other and both will serve plenty of time in prison. Other games are also benchmarked against naive and cooperative agents vastly outperforming them. This is a fantastic paper. Make sure to check it out in the video description for more details. I found it to be very readable, so do not despair if your math kung fu is not that strong. Just dive into it. Videos like this tend to get less views because they have less visual fireworks than most other works we are discussing in a series. Fortunately we are super lucky because we have your support on Patreon and can tell these important stories without worrying about going viral. And if you have enjoyed this episode and you feel that eight of these videos a month is worth a dollar, please consider supporting us on Patreon. One back is almost nothing but it keeps the papers coming. Details are available in the video description. Thanks for watching and for your generous support and I'll see you next time.