culture trumps ethnicity! – intra-generational cultural evolution and ethnocentrism in an...

Culture trumps ethnicity! – Intra-generational cultural evolution and ethnocentrism in an artificial society, David Hales and Bruce Edmonds, Dec 2015, 1

Culture trumps ethnicity!– Intra-generational cultural evolution and

ethnocentrism in an artificial society

David Hales and Bruce EdmondsCentre for Policy Modelling

Manchester Metropolitan University


Ethnocentrism or In-group Bias

• Ethnocentrism, and more generally in-group bias, is a widely observed empirical phenomena in human societies having many different aspects and occurring in many different ‘flavours’ (LeVine & Campbell 1972)

• People seem to often divide the population into those who are considered as part of their group or their ‘type’ (what we will call the in-group) and the rest who are seen as outsiders (the out-group).

• Where such distinctions are made there is often a propensity for more positive behaviour towards the in-group than towards the out-group.


Previous Models

• There are a number of abstract models (Axelrod and Hammond 2003; Hammond & Axelrod 2006; Jansson 2013; Roitto 2015) where:– agents are located on a spatial grid and evolve– interaction and reproduction are localised on the grid– agents can not change their behaviour or location– the ethnic marker may change over generations

• In these, agents eventually come to favour their in-group defined by an observable ethnic marker.

• These models focus on long-range, inter-generation dynamics where no intra-generational learning can occur.


The ethno-cultural tag (ECT) model

• We explore within-generation cultural evolutionary processes in non-spatial environments

• Agents do not reproduce or die but rather imitate and innovate their beliefs and behaviours based the results of interactions with other agents

• These other agents can be society wide rather than localised, but are (probably) members of what they consider to be their in-group

• Agents have a (fixed) ethnic marker and a (changeable) cultural marker, so ethnicity-based vs. culture-based cooperation can be explored


Agent Traits (in-group selector)

Agents can only distinguish between other agents by observing their ethnic marker and cultural tagThe in-group selector determines its in-group, as one of:

– those with the same ethnic marker as itself (ethnic); – those with the same cultural tag as itself (cultural); – those with the same ethnic maker and cultural tag (both); – any other agent without restriction (none).


Agent Traits II (strategy)

Agents can hold one of four possible strategy combinations in the donation game that is played:

1) shirk against both the in-group and out-group (ss); 2) donate to both the in-group and out-group (dd); 3) donate to in-group, shirk on out-group (ds); 4) shirk on in-group, donate to out-group (sd).


Model Processes

Each tick all agents do the following as follows:1. Partner Selection: with probability GB select another in its

in-group as self (if there is one) otherwise another agent at random

2. Game Interaction: donate or not depending on strategies and whether other is in- or out-group

3. Imitation: with probability LB select another in its in-group as self (if exists) otherwise another at random, if other’s payoff > its own, copy other’s selector, cultural tag and strategies

4. Innovation: with small probabilities change (a) cultural tag to a random other and (b) change one of its strategies or selector


Model Parameters


Measures on the model

• All measures are a float in [0, 1] and are averages (over 10 runs) of these calculated over the last 1000 ticks of each 3000 tick run


Some Typical Runs

(a) shows domination of the population by the cultural selector after initial domination by both. (b) shows an oscillation between the two. Notice that when sb is high ie is low. (c) shows a more typical run in which sc dominates. (d) shows a run where sb comes to dominate. (all NE =2, GB=1, LB=0).


Cultural Tag GroupsSimulation Time

Diff

eren

t Cul

tura

l Mar

kers


Donation Rate (dr) for NE=1

Surface plot over parameter space of GB and LB. High cooperation occurs for low LB and high GB (learn from anybody, interact only within group). Cases NE=2 and NE=4 were almost identical.


NE=1, selectors and strategies

in-group selector none cultural ethnic both

av 0.003 0.443 0.002 0.552

sd (0.000) (0.264) (0.000) (0.264)

In-group / out-group strategies

ss ds sd dd

av 0.053 0.875 0.006 0.067

sd (0.003) (0.016) (0.002) (0.015)


NE=1, 2, 3 cases (GB=1, LB=0)

With bigger NE, inter-ethnic donation rates increase, and the cultural selector increasingly dominates the both selector, but rest is very similar

NE dr ie sn sc se sb ss ds sd dd1 0.926 0.000 0.003 0.443 0.002 0.552 0.053 0.875 0.006 0.067

0.003 0.000 0.000 0.264 0.000 0.264 0.003 0.016 0.002 0.0152

0.917 0.392 0.002 0.778 0.003 0.218 0.061 0.872 0.005 0.063

0.008 0.117 0.000 0.236 0.000 0.236 0.007 0.012 0.001 0.0134

0.921 0.725 0.002 0.963 0.003 0.033 0.057 0.880 0.005 0.058

0.007 0.014 0.000 0.019 0.000 0.019 0.006 0.013 0.001 0.009


NE=1, 2, 3 cases (GB=0.5, LB=0.5)

Similar picture with lower over-all donation and more SS strategies. With bigger NE, inter-ethnic donation rates increase, and the cultural selector increasingly dominates the both selector.

NE dr ie sn sc se sb ss ds sd dd1 0.324 0.000 0.002 0.619 0.002 0.379 0.366 0.630 0.001 0.003

0.018 0.000 0.001 0.290 0.000 0.290 0.037 0.037 0.000 0.0002

0.312 0.426 0.002 0.840 0.002 0.157 0.387 0.610 0.001 0.003

0.021 0.101 0.001 0.210 0.001 0.210 0.042 0.042 0.000 0.0004

0.316 0.725 0.002 0.960 0.003 0.037 0.381 0.616 0.001 0.003

0.013 0.009 0.001 0.014 0.000 0.014 0.027 0.027 0.000 0.000


Inter-ethnic donation rate and prevalence of “both” selector (NE=2)

(left) shows inter-ethnic donation rates (ie). (right) shows both prevalence of “both” selector


Dominating Model Process

On inspection of many runs the following two processes seem to dominate the dynamics:• By chance a new “seed group” of two mutual

cooperators appears, these have a high mutual donation and hence are imitated by others; the group grows fast producing a surge of whatever kind of selector were in the seed individuals

• After a while the group is “infected” by defecting individuals who receive but do not donate, the payoff of agents in the group gradually diminishes and eventually individuals copy a new group


General Observations of the Model

• High donation rates occur when game interaction is biased towards the in-group (GB ≈ 1) and learning is population wide (LB ≈ 0).

• In general, cultural groups “trump” ethnic groups and no ethnocentrism emerges. Most agents come to ignore the ethnic marker in defining their in-groups

• In a significant minority of circumstances a form of ethnocentrism does emerge based on in-groups defined by both cultural tag and ethnic marker.

• Suggests hypothesis: that group-based cooperation/discrimination is a result of cultural adaptation and that ethnic-based cooperation occurs only as a special kind of culture-based cooperation


Interpretation Warning!

Real people in real societies do not change their beliefs and behaviours based on simple imitation or random changes. People are attached to particular beliefs and practices for many reasons other than individual benefit. In fact they may be the basis of identity itself and may be held even when they are of no benefit at all. Social behaviours and beliefs result from a complex interplay of upbringing, personal experience, social expectations and norms and are not only the result of adaption of strategy and the basis of judging who is “in-group”. Cultural groups may fall as well as rise, your social capital is at risk if you do not keep up your social obligations. Membership of any cultural or ethnic group is subject to terms and conditions. See website for details.

This model merely tests assumptions about the necessity for a genetically-determined ethnic bias and explores how cultural

mechanisms might be responsible.


The End!

David Hales: http://davidhales.comBruce Edmonds: http://bruce.edmonds.nameCentre for Policy Modelling: http://cfpm.org

The paper is at: http://cfpm.org/discussionpapers/152The model is available at: http://openabm.org/model/4744These slides are at: http://slideshare.net/BruceEdmonds

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