Slime mould, simple rules and the politics of self-organisation

February 15, 2010 — Ben Ramalingam

“Copying nature’s ideas allows people to harness the power of evolution to come up with clever products. Now a group of researchers has taken this idea a step further by using an entire living organism—a slime mould—to solve a complex problem. In this case, the challenge was to design an efficient rail network for the city of Tokyo and its outlying towns.”

So begins an article in last months Science magazine, covering research by Toshiyuki Nakagaki of Hokkaido University and Mark Fricker of the University of Oxford. The study asked whether slime mould – a life form with no brain or central nervous system – could solve a problem usually faced by the best engineers and transportation planners in the world. Their answer is a fantastic illustration of the potential of self-organisation. But as will be argued later, this potential needs to be handled with care, not least because of the scope for political and ideological manipulation of these ideas.

Slime moulds are unusual life forms — neither plant, nor animal nor fungus. The basic slime mould ‘unit’ closely resembles an amoeba, and they are found on woodlands in dark, damp, northern-temperate zones. When foraging, a slime mould will put out feelers, creates nodes and branches, and grow outwards as an interconnected network of tubes, growing up to 25cm wide. As they explore forest floors, they have to constantly trade off the cost, efficiency and resilience of this expanding network. Scientists believe they do so by following simple rules to travel, solve problems, and adapt to environmental conditions. As the purpose of these slime networks is to link food sources together and to transport nutrients around as efficiently as possible, there is an obvious analogy with human transportation networks. The Japan-UK research team set out to find out exactly how similar the processes were. The results were startling.

The scientists tested the slime mould’s capacities by putting oat flakes (a particularly favoured food of slime moulds) in a pattern that represented the positions of cities around Tokyo. Initially, the mould moved so it was arranged evenly around the flakes. But within hours, it began strengthening some nutrient tunnels and connections, while others disappeared. After just one day, the slime mould had built a network of nutrient-carrying tubes, with a overall pattern that bore a striking resemblance to the Tokyo rail system.

Not only had the mould created the shortest possible network that could connect all the cities, but it also included redundant connections that allow the mould (and the real rail network) to have resilience to the accidental breakage of any part of it. The slime mould network, in other words, had similar costs, efficiencies and resiliencies to the human version. Similar research has also been done in the UK, by researchers at the University of the West of England, who used slime mould to accurately model the UK motorway system. As Ed Yong of Science Bloggers has put it:

The mould’s abilities are a wonder of self-optimisation. It has no sense of forward-planning, no overhead maps or intelligence to guide its moves. It creates an efficient network by laying down plasmodia indiscriminately, strengthening whatever works and cutting back on whatever doesn’t. The approach seems as haphazard as a human planner putting railway tracks everywhere, and then removing the ones that aren’t performing well. Nonetheless, the slime mould’s methods (or lack thereof) produced a network with comparable cost, efficiency and tolerance for faults to the planned human attempts…

However, this doesn’t mean that we all need to go foraging for slime moulds in dank northern forests in the hope they will help us with complex project designs. As an Economist article argues:

Of course, [the researchers are not] suggesting that rail and road networks should be designed by slime moulds. What they are proposing is that good and complex solutions can emerge from simple rules, and that this principle might be applied elsewhere. The next thing is to discover and use these rules to enable other networks to self-organise in an “intelligent” fashion.”

As Ed Yong shows, this can be achieved through computer models, which can be used to explore network strengths in considerable detail:

Tweaking the specific conditions of a model produced networks that were very similar to those of both [slime mould] and Tokyo’s actual rail system. Tweaking it further allows us to boost the system’s efficiency or resilience, while keeping its costs as low as possible. This, perhaps, is the engineering of the future – a virtual system inspired by a biological one that looks a lot like a man-made one…”

The area of public policy that has seen perhaps the greatest application of these principles is traffic management, where there is a well-documented movement away from over-management and towards setting minimum rules for self-organising behaviour (watch out for an forthcoming Aid on the Edge post on this topic). But there have also been applications in large-scale infrastructure projects, urban development, decentralisation projects in national government, crisis response planning, epidemics modelling, and analysing knowledge flows in organisations.

All of these areas have relevance for aid agencies working on development and humanitarian issues. But a cautionary note must be struck. It is important not to get carried away with the idea of self-organisation – instead what is needed is to critically engage with the possibilities in an objective fashion. Otherwise, as Dave Snowden put it recently on KM4Dev, we may fall prey to “…the ideological use of ‘self-organisation’ and ’emergence’…”

While self-organisation can and does happen in a variety of social, economic and politcial realms, its use in public policy can increasingly be described as politically motivated “bad science”. In broad terms, such arguments hinge on using complexity principles to argue for less government and more free markets as a means to achieving economic or societal goals.

How to guard against such applications? Well, first, there is little evidence for such political statements in the serious complexity literature. This is certainly one way of warding off the inappropriate use of these ideas. But then such political claims seldom need evidence – an illusion of scientific authority will usually suffice.

Perhaps the strongest arguments against such politically-driven uses is to carefully illustrate the range of situations where self-organisation is neither good nor desirable. The credit crunch is a now-classic example of how a lack of regulation can lead to serious problems and the need for extensive government intervention down the line (see an earlier post on the financial crisis through a complexity lens). And as I have argued elsewhere:

A study of the role of self-organisation in the Rwandan genocide (Bhavnani, 2006) argues that the levels of mass participation can be partly explained by a self-organising emergence of a violence-promoting norm among the Hutu community, such that killing Tutsis became the norm among members of the ethnic group. This self-organisation… was driven by complex patterns of interactions among individuals forming Rwandan society. The study concludes that the frequently attributed causes of the genocide – including the death of the Rwandan president in a plane crash, the ethnic tensions and the post-war culture in Rwanda at the time – are at best partial explanations that need to be related to the bottom-up collective processes of violence through which the genocide unfolded.”

It should be clear that the self-organised structures and patterns that emerge from a mass of complex interactions need not necessarily be ‘good’ for all those involved. Self-organisation is itself a neutral concept, and one that cannot be simply applied to any situation where government plays a minimal role. In fact, most social complexity theorists would argue that the key issue is one of balance – of identifying how planners, strategists, managers and front-line staff might better understand and work with self-organising processes and systems in ways that might lead to beneficial changes down the line.

So watch the slime mould, by all means, but remember that we are dealing with rather different problems and issues when we are working in complex social human worlds. And anyone who says different is more than likely selling you something.

(Really dedicated readers can watch a slime mould network forming on YouTube, along with various fungal activities.)