Comments on: Playing by the same rules reduces the differences between humans, chimps and monkeys

By: SP

SP — Tue, 08 Feb 2011 09:26:19 +0000

Looks to me like de Waal is reading far too much into his data. The strong result is that the predominant ‘strategy’ for each species is entirely different: none for capuchins, matching for chimps and hare-hare for humans. Add to that Daniel’s excellent point that there are two equilibria — one of which might simply never have been observed by the human participants (I only mention humans as there is no evidence that the non-human participants were even looking) — and this seems like strong evidence for difference rather than similarity. Am I missing something?

(Superb site by the way Ed. Your stem cell timeline article the other day was a masterpiece.)

By: Steve Pratt

Steve Pratt — Tue, 08 Feb 2011 00:31:40 +0000

What was the sampling frame for recruitment of the non-human primates? Were they WEIRD? That could explain an difference.

Do you really “recruit” chimpanzees and capuchins (the two in Night at the Museum seem quite clever)?

By: jami

jami — Tue, 08 Feb 2011 00:01:12 +0000

Psychasm- i believe it says that humans and primates alike sat next to their partners. it also stated they were shown the results after each round.

By: Psycasm

Psycasm — Mon, 07 Feb 2011 22:43:19 +0000

How was the game played? We’re the humans separated? Did they know that another human helped them when they chose stag-stag? The same for chimps – did they know another chimp was playing? Did they get feedback?

I think, without these details, it’s hard to draw conclusions like ‘we behave similarly’. While there’s only 4 outcomes, after I make my decision (hare / stag) it’s a 50/50 chance that my partner will choose the same. If this is the case, it may simple represent learning under positive reinforcement. To draw social conclusions, social context is needed.

By: Ed Yong

Ed Yong — Mon, 07 Feb 2011 22:36:07 +0000

@Daniel – Yes, there are two equilibrium outcomes – Stag-Stag and Hare-Hare. The “match” category means that the individuals played a mix of the two strategies.

By: Stephan Zielinski

Stephan Zielinski — Mon, 07 Feb 2011 21:30:06 +0000

Couldn’t find a photo of a chimp with that same haircut?

(I’d have to go get a shot of a turkey vulture.)

By: Daniel Kuehn

Daniel Kuehn — Mon, 07 Feb 2011 20:59:35 +0000

I’m not sure what to make of this… I think we generally expect the hare-hare option as a sub-game perfect equilibrium, right? If higher level coordination between the parties and enforcement is possible (it’s unclear here if it is), then stag-stag may emerge.

With that in mind, I would make less of the relative similarity in stag-stag, and more of the stark difference in hare-hare. The fact that humans land on the sub-game perfect equilibrium seems to suggest that something very different is going on in humans.

What exactly is match-match? Does that just mean that there’s a mixture of stag-stag and hare-hare in a sequential set of games? This could suggest chimps have basic tit-for-tat logic, which would be interesting. Anyway – I don’t feel I have a full understanding of how these outcomes are categorized, but the match-match and hare-hare outcomes strike me as being more interesting than the stag-stag outcome.

By: HP

HP — Mon, 07 Feb 2011 20:10:37 +0000

I wonder if they’d get different results offering the humans fresh fruit instead of coins.

I could go for a grape or a nice bit of melon right now.