Prisoner's Dilemma on game show Golden Balls

This game has multiple Nash equilibria and cheap talk is allowed, so correlated equilibria are possible. Here's how you implement a correlated equilibrium if your opponent is smart enough:

"We have two minutes to talk, right? I'm going to ask you to flip a coin (visibly to both of us) at the last possible moment, the exact second where we must cease talking. If the coin comes up heads, I promise I'll cooperate, you can just go ahead and claim the whole prize. If the coin comes up tails, I promise I'll defect. Please cooperate in this case, because you have nothing to gain by defecting, and anyway the arrangement is fair, isn't it?"

he merely has the option to hurt him out of spite.

Merely? Never underestimate the power of Spite.

The changed payoff matrix makes this unlike the Prisoner's Dilemma even without the addition of communication; more like a restricted bargaining game. One noteworthy difference from the Prisoner's Dilemma is that this game lacks a pure Nash equilibrium.

Edit: Apparently not quite; see below.

I love the bit at the end where Ibrahim (market trader) says it's "the hardest money I've ever had to work for" and Nick (charity worker) jokes "he obviously hasn't worked in the charity sector to try and get money", then the look on Nick's face when Ibrahim says he's going to respray his yacht!

I felt that Nick displayed a good mix of hot and cold rationality.

The next contestant needs to say:

"I'm going to choose steal. If you choose split, I'll give you 25 percent after the show. I promise."

WTF why did he (the precommiter) choose split after all?

The WHOLE point is to change it from a difficult decision with close outcomes to one where split is the only choice with positive utility (the chance that other person will keep their word).

To be a little technical, this is not actually prisoners dilemma, because they are allowed to communicate. The whole point of prisoners dilemma is that they cannot communicate, and thus, must choose to cooperate or defect based upon their knowledge of nash's equilibrium alone.

Although this is honestly quite an interesting solution to this kind of problem. I'll be using it the next time I'm offered a situation similar to this.

Anyone watch this show regularly, and know how Split/Steal normally plays out?

I can say, without hindsight interfering, that this strategy would not have worked on me. Because I can explain exactly what I was thinking as it happened.

You see, when I see someone alter the rules of a game, my instinct is that they are trying to do so for their own gain, and thus are not altruistic. Thus I immediately assumed the promise was a lie (which was right), and that he would not be splitting the money with me (which was wrong).

The question then becomes rather simple. My choices are to choose SPLIT, receive $0, and reward the treachery, or choose STEAL, still receive $0, and punish the treachery. Obviously, the latter is more valuable to me.

Now, in the short time required, I did not have time to check if my assumptions were correct. But let's say they aren't. The most likely way for me to be wrong would not be that he wasn't lying, but that he was going to choose SPLIT. Well, that's still a winning outcome for me. And if I feel guilty for winning all the money, I can always split after the fact with him. So that's not a problem either. The only option that is a possible problem is if he's telling the entire truth. But I see this as highly unlikely, as what does he have to gain from splitting after the fact rather than just using the balls?

I honestly was surprised that this worked. I actually thought the other guy was foolish for choosing SPLIT until the reveal. As I do not know the other possible solutions I cannot say the first guy's solution was rational, but I am fairly confident in saying the second guy's decision was not.

Watch and see how one player deals with this.

Wow. That guy is a loony! I'd have walked away with a lot of money in that game (in the other guy's shoes).