I think the first time I heard about it might have been on this Planet Money episode: https://www.npr.org/templates/transcript/transcript.php?storyId=615621554

I think the first time I heard about it might have been on this Planet Money episode: https://www.npr.org/templates/transcript/transcript.php?storyId=615621554 https://www.npr.org/templates/transcript/transcript.php?stor... But I'm not really sure. This Google search links to a bunch of papers on the subject. It's a well explored area of research: https://www.google.com/search?q=repeated+prisoner%27s+dilemma+study+simulation+best+strategy https://www.google.com/search?q=repeated+prisoner%27s+dilemm...