EHBEA Day Three: Punishment, Parochial Altruism, and Cooperative Institutions

The third day of the EHBEA conference in Amsterdam brought several highly interesting talk on the evolution of cooperation, altruism, and punishment, my main areas of interest. Unfortunately, I am a bit strapped of time, so I will only summarise the talks most important to me.

Altruistic Punishment in Public Goods Games

The day commenced with a keynote by Simon Gächter of the University of Nottingham. Gächter, together with Ernst Fehr, pioneered the use of punishment in Public Goods Games1 and has been a major proponent of altruistic punishment as a solution to free-rider problems.

Gächter recapped his research program of the last ten years, showing that altruistic punishment induces cooperation, occurs widely,2 and increases total pay-offs from cooperation in the long term.3 In particular, he argued that, though abstract, Public Goods Games are psychologically rich, indicated by the anger trigger by free-riding.

A major challenge to the ecological validity of Gächter’s experiments comes from the fact that they are conducted under conditions of full anonymity, which some have argued opens the door to unrealistically harsh punishment. New data from ongoing experiments which he presented counter this criticism. When participants meet each other before playing the games, even for a short moment, this increases cooperation even in the absence of punishment (but does not stop its gradual decline).

When identifiability and punishment are combined, cooperation increases to near-perfection. At the same time, punishment becomes less frequent than expected; nevertheless it successfully sustains cooperation that would otherwise decline (or so does the threat; some groups never actually punish). This is quite fascinating, because it indicates that in prehistoric small-scale societies, in which members of small communities frequently interacted, punishment would have been a highly cost-effective way of enforcing cooperation.

Social and Individual Information; Prospect Theory

Ulf Tölch of the Humboldt University of Berlin presented findings from experiments on the integration of social and individual information. In a two-phase experiment, individuals first learned about their own accuracy in indicating a target location on a circle. Subsequently, they were presented with a combination of their own guess and either more or less accurate social information (or a combination of the latter two).

Tölch found that when integrating two bits of social information, players made bayes-optimal decisions, i.e. weighted the integration of information for source reliability. When integrating their own information with other sources, however, failed to do this. In particular, it appeared that people who were very accurate themselves overestimated their own accuracy. Using fMRI scans, the researchers found evidence that some people – who acted Bayes-optimal – were able to overwrite individual information.

Dave Mallpress presented a model for the evolution of the fourfold pattern of risk preference described by prospect theory4 In a variable, but autocorrelated environment, agents dependent on energy levels were offered the choice between a (more or less risky) gamble and a safe option. Whether agents in the model chose to gamble depended on the state of the environment in a fashion similar to the fourfold pattern of prospect theory: gamble in extremely bad environments, but play it safe in extremely good ones; mostly gamble in quite good environments, but mostly play it safe in quite bad ones.

Parochial Altruism

Antonio Silva of the University College London presented two experiments out of a larger research program on parochial altruism and inter-group conflict in Northern Ireland. This research program is particularly interesting because it aims to maximise the ecological validity of experiments. The methods Silva described look very promising to me.

Parochial altruism is the idea that inter-group conflict gives rise to increased in-group altruism and decreased out-group altruism. Northern Ireland with its long-lasting conflict between Catholics and Protestants naturally lends itself to studying this phenomenon. Silva and his colleagues used several methods, including donations (of endowments to neutral, Catholic, or Protestant charities) and a lost-letter paradigm, in which letters were addressed to either Catholic or Protestant neighborhoods and ‘lost’.

The lost-letter paradigm found evidence for reduced out-group altruism – Catholic letters ‘lost’ in Protestant neighbourhoods were returned less often than Protestant and neutral letters (and vice-versa). Donations to in-group, out-group, and neutral charities were predicted mostly by socio-economic variables; a sectarian threat variable was only negatively correlated with out-group donations. Hence both measures found evidence for reduced out-group altruism, but not increased in-group altruism, and thus not for parochial altruism.

From Small-Scale to Large-Scale Societies

Simon Powers of the University of Lausanne presented a model for the evolution of punishment institutions. He argued that while most theories (such as Gächter’s) assume that social interactions are uncoordinated, “in real groups [they] tend to be regulated by institutions.” Powers explicitly bases his models for the bottom-up creation of institutions on the work of Elinor Ostrom, who also pioneered research into altruistic punishment.5

Power’s model is based on a modified Public Goods Game. Instead of making punishment decisions individually, agents first decide on the share of the public good they would like to see used for punishment (vs. investment), and then play the PGG. Institutional rules are formed by taking the mean preference of cooperators and defectors for sanctioning. The dynamics of the model are thus governed by individual preference for punishment and propensity to cooperate, defect, or not participate in the PGG.

When most of the public good is used for investment, cooperators can invade, but when investment gets too high, asocials take over, thus leading to cycling dynamics. When spatial structure is introduced in the model, however, where migration is dependent on the level of cooperation within a group, cooperators can take over a group. The group size then expands and cooperation as well as institutional sanctions stabilise at high levels.

Power’s model is interesting for multiple reasons. I was particularly intrigued that it considers migration rate as a variable dependent on cooperation levels (rather than as a constant, which I’ve seen in many group-level selection models). I’d also be curious to see how such institutional sanctions would fare in behavioural experiments (while being aware that as an evolutionary model, this does not make predictions about contemporary behaviour).

  1. Fehr, E. & Gächter, S. (2000). Cooperation and Punishment in Public Goods Experiments. The American Economic Review, 90(4), 980-94. []
  2. Herrmann, B., Gächter, S., & Thöni, C. (2008). Antisocial punishment across societies. Science, 319(5868), 1362-7. DOI: 10.1126/science.1153808. []
  3. Gächter, S., Renner, E., & Sefton, M. (2008). The long-run benefits of punishment. Science, 322(5907), 1510. DOI: 10.1126/science.1153808 []
  4. Kahneman, D. & Tversky, A. (1979). Prospect Theory: An Analysis of Decision Under Risk. Econometrica, 47, 263-91. []
  5. Ostrom, E., Walker, J., & Gardner, R. (1992). Covenants With and Without a Sword: Self-Governance is Possible. The American Political Science Review, 86(2), 404-17. []
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EHBEA Day Two: Competitive Altruism and Competition for Partners; also a lot of masculinity.

Today was the second day of the EHBEA conference in Amsterdam. Unfortunately, I was forced to miss the keynote, but there were some very interesting presentations. In particular the work by Gilbert Roberts on competitive altruism is very promising, and it was great to hear about it. Arno Riedl also reported some very interesting (and related) work on competition for partners as a driver of cooperation.

Gilbert Roberts on Competitive Altruism

Gilbert Roberts of Newcastle University presented models and empirical evidence on competitive altruism, which is the idea that by behaving altruistically, individuals provide information to potential cooperation partners. Competition for more appealing cooperation partners then drives reputation-enhancing (altruistic) behaviour.van Vugt, M., Roberts, G., & Hardy, C. L. (2005). Competitive Altruism: Development of Reputation-based Cooperation in Groups. In R. I. M. Dunbar & Louise Barrett, Handbook of Evolutionary Psychology (pp. 1-28). Oxford, UK: Oxford University Press.

Competitive altruism has been tested in two-stage economic games. The first stage allows for building a reputation as a good cooperator (e.g. Public Goods Games, PGG). Then, during the second stage players can choose partners to play paired games with. As such, competitive altruism is in particular a rival theory to indirect reciprocity. Roberts reported findings that in the PGG, competitive altruism drives contributions more than indirect reciprocity does.

Based on these findings, Roberts proposed an agent-based model of reputation building with three decision points:

  • Stage 1: Build reputation or not?
  • – choose partner according to reputation or not –
  • Stage 2: Cooperate or defect on partners? (or don’t play)

In simulations, reputation and cooperation can evolve (as can choosing, but at lower levels), at least for some parameters. As the number of meetings increases, higher levels of reputation building are observed.

Child Mortality and Reproduction

Caroline Uggla of the University College London proposed to investigate why health technologies are not adopted in developing countries even when they are available based on parental investment theory, and bringing together human behavioural ecology and public health. Using data from the Demographic Health Surveys, she showed that parental investment theory predicts how several mother- and child-status variables predict whether children will receive curative and preventative treatments. For example, older mothers invest more in their children. However, some puzzles remain. The positive effect of mothers’ age, for instance, appears contradictory with the negative effect of birth order. Also, sicker children are more likely to get curative, but less likely to get preventative treatments, but it is not clear why.

Paul Mathews of the London School of Hygiene and Tropical Medicine (LSHTM) presented evidence from two studies on reproductive plasticity, i.e. the idea that reproduction is dependent on environmental factors. In two experiments, he found that priming subjects with their own mortality increases the ideal number of children in men, but not women; and increases the desire for childlessness in women, but not men (furthermore, priming subject with dental health increases their desire to remain childless – a control condition gone hilariously wrong).

Susan Schaffnit, also of the LSHTM, presented findings on parent-child proximity and women’s reproductive fitness in Europe. She set out to test hypotheses about two conflicting theories. On the one hand, cooperative breeding theory predicts that living with parents increases reproductive fitness. On the other hand, local resource competition theory predicts that being around relatives (although more often siblings than parents) decreases reproductive fitness. Schaffnit’s analysis of data from Europe found support for both hypotheses: living parents are associated with younger age at first birth, but living with them has a negative effect. Women who move away from home later also have a higher probability of remaining childless.

Facial Characteristics and Ultimatum Game Behaviour; Female Economic Dependence

I missed the first talk of this session, by Daniel Tayler on the excludability of public goods, and was unfortunately distracted during the third by Hannah Cornish on systematicity of culture.

Poppy Mulvaney of the University of Bristol reported on two studies investigating the effect of receiver’s facial characteristics on proposer behaviour in the Ultimatum Game. In a UK sample, formidability – associated with physical dominance – predicted offers, but trustworthiness did not. However, in a second sample in the United States, trustworthiness, but not formidability predicted fair offers. Notably, the two samples did not differ in their personality ratings for the faces, thus leaving open the question as to why different facial characteristics would predict proposer behaviour.

Michael Price of Brunel University proposed a model of morality judgements on promiscuity that includes female economic dependence. This hypothesis is consistent with the idea that opposition to promiscuity is to promote paternity certainty. Indeed, female economic dependence somewhat predicted attitudes towards both male and female promiscuity in a model also including sex, religiosity, and conservativism. Price argues that religiousity and conservatism are only proximate predictors, i.e. that their anti-promiscuous stance requires explanation, and sees evolution in an environment of high female economic dependence as an answer.

Arno Riedl on Competition for Partners as a Driver of Cooperation

Arno Riedl of Maastricht University presented experimental findings that competition for partners can drive cooperation among strangers. The underlying question of this study is what it needs to enforce the social norms of cooperation in societies with infrequent interactions. This was tested using a very interesting modification of the classic Prisoners’ Dilemma that allowed Riedl his collaborator Aljaz Ule (of the University of Amsterdam) to tease apart the effects of exclusion and partner choice.

Subjects played repeated PD games, paired up in groups of three. They all learn about the most recent interactin of each subject in the triplet. In each triplet, at most one pair of subjects can play the PD (which is strictly preferable over not playing), thus inducing partner competition. Riedl and Ule then varied the condition under which pairs are formed:

  • baseline: formed randomly (no partner refusal, no competition)
  • refusal: formed randomly, but each subject can refuse to play
  • competition: subjects indicate acceptable partner, if feasible a pair is formed

Cooperation rates in round one were very similar (43/43/38%), but diverged strongly across 60 iterations: While baseline and refusal condition cooperation fell to around ten percent in a monotonic decrease, it steadily increased to almost fifty percent in the competition condition. Refusal was rare throughout.

Interestingly, in the competition condition, two types of groups emerge: non-cooperative and fully cooperative groups. This difference appears to be driven by the exclusion of previous defectors. In the refusal condition, refusal was rare (2%). Non-cooperative groups in the competition condition also showed rather low levels of exclusion of previous defectors (15%), which markedly set them apart from cooperative groups, whose members refused to cooperate with defectors 50 percent of the time. Riedl concluded that community enforcement of cooperation norms is possible, but requires competition. The mechanism at work is the exclusion of revealed defectors.

Recalibration Hypothesis; Evolution of Masculine Faces

Lars Penke of the University of Edinburgh tested the recalibration hypothesis, which argues that the effects of genetic variation on personality (or behaviour more broadly) is mediated by morphology (e.g., a proposal that narcicissm is founded in objective attractiveness). Using several anthropomorphic measures and third-party rating, Penke found only scattered associations with personality traits. He concludes that the recalibration theory explains only little variation in social personality traits, and only in men. Previous studies were likely confounded, e.g. by using self-reported attractiveness (which might itself correlate with traits like narcicissm).

Iris Holzleitner of the University of St. Andrews presented a model linking morphological masculinity and attractiveness. Two contrasting hypotheses have been put forward to explain the evolution of masculine faces. One is that they are a handicap to signal health, and evolved due to intersexual selection (i.e. choosy women looking for healthy males). In contrast, masculine faces might have evolved under pressure of intrasexual competition as a cue to dominance. Holzleitner’s model, which takes into account facial masculinity (as well as height and weight), finds that masculinity has a significant effect on social dominance, but not health; and an effect on attractiveness only via social dominance. This suggests that masculinity evolved as an intrasexually selected trait.

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EHBEA Conference: Joe Henrich on Culture-Gene Coevolution

The Vrije Universiteit Amsterdam is hosting the annual conference of the European Human Behaviour and Evolution Association (EHBEA) until Wednesday. I am attending and will try to cover as much of the conference as possible on this blog.

Before the official kick-off of the conference on Monday, Joe Henrich of the University of British Columbia in Vancouver presented a first keynote tonight. Henrich is trained as an anthropologist (and aviation engineer!), but has collaborated widely with economists like Ernst Fehr and Colin F. Camerer and psychologists like Mark van Vugt, who convened the session. Henrich has prominently pointed out the fallacy of basing behavioural research purely on ‘WEIRD’ (Western, educated, industrialised, rich, democratic) people, and advocated a cross-cultural approach.1

In his talk on the ‘Culture-Gene Coevolutionary Origins of Human Cooperation’, Henrich aimed to root out remnants of the idea that ecological and cultural explanations are conflicting. Rather, as he said, “cultural evolution provides a set of psychologically and evolutiarly grounded processes that can plausibly create patterns of ecological adaptation”.

This view as profound implications for the foundations of evolutionary psychology. There is, for example, the attempt to establish conditions in the ‘Environment of Evolutionary Adaptiveness’ (EEA). However, culture-gene coevolution implies that recurrent features of selective environments are themselves the product of cultural evolution.

With regards to the evolution of human cooperation, Henrich presented five “challenges for a theory of large-scale human cooperation”:

1) Why is the scale and intensity of human cooperation so much greater than other mammals – at least in some societies?
2) Why does the scale and intensity of cooperation and collective action vary so dramatically across a) societies and b) domains?
3) Why has the scale and intensity of human cooperationa nd collective action expanded so dramatically in the last 10,000 years?
4) Why do the mechanisms that sustain cooperation also sustain non-cooperative behaviour (food taboos, sexual practices, rituals), including maladaptive stuff?
5) Why do the ‘sustaining mechanisms’ vary across societies?

Over the last decade or two, a variety of cultural evolutionary models have been proposed that can sustain varying degrees of large-scale cooperation. Henrich singled out three of these families of models in particular:

1) Diffuse costly punishment (which can sustain norms).2
2) Positive indirect reciprocity linkage (which can sustain norms).3
3) Signaling (which can stabilize costly punishment, and maybe by that way also norms).

Because all of these models have multiple stable equilibria, they are unlikely to explain genetic evolution. Rather, “these are some of the tricks that cultural evolution can use to exploit our evolved psychology”. However, Henrich’s own field work (among horticulturist-fishers on a Fijian island) indicates that de facto, none of these models explain norm enforcement in existing societies.

Henrich and his colleagues observed that on Yasawa Island, “negative indirect reciprocity stabilizes social norms”. The existing “reputation system harnesses simmering jealousies, past grievances, status rivalries, and desire to steal to sustain costly norms, including cooperation.” When a villager breaks a norm (either cooperative or not), this creates an opportunity for others to act against the violator, e.g. by means of theft, damaging property, or physical violence. These incidents are either not investigated, or at least associated with much less reputational damage than when committed against norm-abiding neighbours.

From a methodological perspective, the lesson is that “evolution is smarter than us”: Evolutionary models should be based on observations in the field. Or, as Henrich puts it, we “we need to go out in the world and ask the right questions”. A second point is that the focus on the evolution of cooperation could be misguided. Rather, we need to understand social norms, cooperative or not, and mechanisms by which they are enforced.

  1. Henrich, J., Heine, S. J., & Norenzayan, A. (2010). The weirdest people in the world?. The Behavioral and Brain Sciences, 33(2-3), 61-135. DOI: 10.1017/S0140525X0999152X []
  2. Boyd, R. & Richerson, P. J. (1992). Punishment Allows the Evolution of Cooperation (or Anything Else) in Sizable Groups. Ethology and Sociobiology, 13, 171-95. DOI: 10.1016/0162-3095(92)90032-Y []
  3. Nowak, M. A. & Sigmund, K. (2005). Evolution of indirect reciprocity. Nature, 437(7063), 1291-8. DOI: 10.1038/nature04131 []
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