Looking again at the payoff table, you may notice that if the other player co-operates, you are better off defecting and making them the sucker. Then again if the other player defects, you are also better off defecting, to avoid the sucker payoff yourself. So you are better off playing 'D' no matter what happens. That's the strategy which gets you the highest score in the game you've just played (go back and give it a go if you're in doubt).
The rationale for always defecting seems clear and straightforward. The problem is that both players will see this line of reasoning, both defect, and each get just 1 point per round; much less than if they had co-operated.
Here is a puzzle that demands a closer look: If the rational choice is always to defect, then why do rational people ever co-operate with each other?
Think about how the "always defect" strategy would work in real life. If you broke promises and exploited people whenever you had the chance, you'd quickly run out of friends, and this would severely restrict the things you could do. Defection in real life can be irrational because other people will respond to your actions, and they will not respond well to defection.
You saw on the last page that "always defect" works when the other player chooses randomly. However, not all players are random. On the next page, we will try playing against a different kind of player.
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