A talk at the workshop on "Thinking toys (or games) for commoning, Basel, 5/6 April, Switzerland. This describes a simple model of anonymous donation of resources, with minimal group structuring. Am open-access paper on this model is at: http://cfpm.org/discussionpapers/152 The model can be freely downloaded from: http://openABM.org/model/4744

1. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 1
A Simple Model of Group Commoning
Bruce Edmonds
Centre for Policy Modelling
Manchester Metropolitan University

2. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 2
Tags and Groups
THE SNEETCHES
by Theodor Geisel (1961)
(aka. Dr. Seuss)
Now, the Star-Belly Sneetches
Had bellies with stars.
The Plain-Belly Sneetches
Had none upon thars.
Those stars weren't so big. They were really so small
You might think such a thing wouldn't matter at all.
But, because they had stars, all the Star-Belly Sneetches
Would brag, "We're the best kind of Sneetch on the beaches."
With their snoots in the air, they would sniff and they'd snort
“We'll have nothing to do with the Plain-Belly sort!"
And whenever they met some, when they were out walking,
They'd hike right on past them without even talking.
…

3. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 3
In-groups
• There is a lot of research that humans cooperate
more with what they perceive is their group
• But they are flexible about how they define who is
in their ‘in group’ and who is not (the ‘out-group’)
• Even when people are arbitrarily divided into
groups, they still give preference to their group
• The effect is even stronger when there is some
commonality (culture, occupation, location etc.)
• With strangers, one can only guess who is in ones
in-group through observable signals (accent,
clothes, etc), these we call ‘tags’
• Tags need not be hard-wired to behaviour

4. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 4
A simple  simulation model…
Here I present a ‘simple’ agent-based simulation
which shows a process by which cooperation and
free donation can flourish, even when agents:
• Are selfish, trying to increase their wealth
• Are mutually anonymous, and so can not decide
behaviour from their past dealings with them
• Agents can choose not to help others without
others knowing this directly
But which assumes that:
• Different groups are recognisable
• One can learn from anyone

5. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 5
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 their
strategy 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 kind of in-group)

6. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 6
The view of agents in the simulation
Each ‘spoke’ is a
group (those with
the same tag)
give to in-group
give to nobody
give to anybody
give to out-group
Colours indicate
type of agent

7. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 7
Dominating Model Process
On inspection of many runs the following processes
seem to dominate the dynamics:
• By chance a new “seed group” of cooperators
appears, these have a high mutual donation and
hence are imitated by others so the group grows
• A cooperative group is “infected” by individuals
who receive but do not give, the payoff of agents
in diminishes and eventually individuals leave
• There are no cooperative groups, everyone is
selfish, the system ‘stagnates’ until a new seed
cooperative group appears

8. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 8
Warnings!
• This is a very simple and abstract model that
shows possibilities only
– It does not show that humans behave this way
• There are many ways in which humans make
cooperate/not decisions (or decide which group
they are in) that are not included in this simulation
• Humans have many other mechanisms to
facilitate cooperation (social norms, memory,
enforceable contracts, social exclusion etc.)
– This just demonstrates some minimal conditions for
cooperative groups to emerge

9. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 9
Conclusions
Free donation can flourish and be sustainable via a dynamic
system of groups – continually forming, growing, dying
…even when agents are selfish, deal with strangers and
non-cooperation can be hidden
But the conditions for this include that agents can:
• See the success of individuals in other groups – openness
• Change groups, if this seems better for them – personal
choice of membership
• Can form completely new groups fluidly – freedom of
association
• Turning selfish within a group is relatively slow – some
group pressure to conform

10. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 10
Acknowledgements
Most of this work was
done by my friend and
long-time collaborator,
David Hales.
For more about him and
his work on tag models
and cooperation see:
http://davidhales.com
Some of this work was
funded by the EPSRC

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Other, more complex, models
1D world of
complex artifacts
whose creation
steps has to be
discovered shared
between agents

12. A Simple Model of Group Commoning, Bruce Edmonds, Basel, Switzerland, April 2018, 12
Centre for Policy Modelling: http://cfpm.org
Bruce Edmonds: http://bruce.edmonds.name
A version of these slides are at: http://slideshare.net/BruceEdmonds
Am open-access paper on this model is at:
http://cfpm.org/discussionpapers/152
The model can be freely downloaded from:
http://openABM.org/model/4744