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Month: June 2012

Tit-for-tat no more: new insights into the origin and evolution of cooperation

The Prisoner’s Dilemma (PD) is the paradigmatic scientific model to understand human cooperation. You would think that after several decennia of analyzing this deceivingly simple game, nothing new can be learned. Not quite. This new paper discovers a whole new class of strategies that provide a unilateral advantage to the players using them in playing the repeated version of the game. In effect, using these strategies one can force the opponent to any score one desires. The familiar tit-for-tat strategy, which so far had been assumed to be the optimal way of playing the repeated game, appears to be just the tip of an iceberg of ‘zero determinant’ strategies which ‘enforce a linear relationship between the two players’ scores’. This is huge and people have already started to discuss the implications. But what puzzles me is the following: The search for an optimal way to play the repeated PD has been going on at least since the 1980s. The best strategies have been sought analytically, and through simulation (see Robert Axelrod’s iterated PD tournaments). And yet nobody discovered or stumbled upon ‘zero determinant’ strategies for more than 30 years of dedicated research. So can we expect a rational but not omnipotent actor to use these strategies? I think the formal answer needs to be ‘yes’ – a rational actor plays the game in the most advantageous way for his/her interests and if zero determinant strategies provide en edge, then he/she needs to (and is expected and predicted to) play these. The alternative would be to impose some limitations to the…

Facebook does randomized experiments to study social interactions

Facebook has a Data Science Team. And here is what they do: Eytan Bakshy […] wanted to learn whether our actions on Facebook are mainly influenced by those of our close friends, who are likely to have similar tastes. […] So he messed with how Facebook operated for a quarter of a billion users. Over a seven-week period, the 76 million links that those users shared with each other were logged. Then, on 219 million randomly chosen occasions, Facebook prevented someone from seeing a link shared by a friend. Hiding links this way created a control group so that Bakshy could assess how often people end up promoting the same links because they have similar information sources and interests  [link to source at Technology Review]. It must be great (and a great challenge) to have access to all the data Facebook and use it to answer questions that are relevant not only for the immediate business objectives of the company. In the words of the Data Science Team leader: “The biggest challenges Facebook has to solve are the same challenges that social science has.” Those challenges include understanding why some ideas or fashions spread from a few individuals to become universal and others don’t, or to what extent a person’s future actions are a product of past communication with friends. Cool! These statements might make for a good discussion about the ethics of doing social science research inside and outside academica as well.

Diesel, cancer and how (not) to report about risk

The BBC reports that diesel exhausts have been declared as causing cancer. That could very well be, but the way the results are reported leaves a lot to be desired. First, look at this bit: Dr Kurt Straif, also from IARC, said: “For most of the carcinogens when there is high exposure the risk is higher, when there is lower exposure the risk is lower.” Hmm, so lower exposure to diesel lowers the risk of cancer?! Lower than what? Than no exposure at all? I presume that this is just an awkward way of saying that the risk increases with the amount of exposure. But then at what point does the risk become ‘significantly’ higher than the risk if not being exposed? When you pass behind a diesel car once a day? When you work behind fuming diesel engines all day long? When you get a single overdose once in your life? Without answers to all these questions, the information that some level of exposure to diesel is related to an increase in cancer risk is pretty useless to me. What is also missing is a crucial comparison to petrol. How does the risk of exposure to diesel compare to the risk of exposure to petrol? Is petrol carcinogenic as well, to a smaller degree, or not at all? Part of the scientific evidence for the carcinogenic effects of diesel is apparently based on observing truck drivers. No details or links to this research are provided, but I wonder how these truck drivers…

Protestants, Missionaries and the Diffusion of Liberal Democracy

A new APSR article [ungated] argues for the crucial role of Protestant missionaries in the global spread of liberal democracy. The statistical analyses tease out the effect of missionaries from the influence of the characteristics of colonizers (Britain, the Netherlands, France, etc.) and pre-existing geographic, economic and cultural characteristics of the states. Interestingly, Protestant missionary influence not only remains a significant predictor of democracy outside the Western world once these factors are controlled for, but it renders them obsolete (which is a big deal because the same institutional, geographic, economic and cultural characteristics have been the usual explanations of democracy diffusion). On the other hand, the patterns in the data are consistent with the plausible mechanisms through which the effect of Protestant missionaries is exercised – the spread of newspapers, education, and civil society. I am sure this article is not going to be the last word on democracy diffusion, but it certainly puts the influence of Protestantism center stage. The major issue, I suspect, is not going to be methodological (since the article already considers a plethora of potential methodological complications in the appendix), but conceptual – to what extent the effect of Protestant missionaries can be conceptually separated from the improvements in education and the growth of the public sphere. In other words, do (did) you need the religious component at all, or education, newspapers and civil society would have worked on their own to make liberal democracy more likely (even if fostered by other channels than Protestant missionaries) . In terms of methodology, it might be interesting…