Ants, algorithms and complexity without management

NAECDeborah M. Gordon, Department of Biology, Stanford University

Systems without central control are ubiquitous in nature. The activities of brains, such as thinking, remembering and speaking, are the outcome of countless electrical interactions among cells. Nothing in the brain tells the rest of it to think or remember. I study ants because I am interested in how collective outcomes arise from interactions among individuals, and how collective behaviour is tuned to changing environments.

There are more than 14,000 species of ants, which all live in colonies consisting of one or more reproductive females, and many sterile workers, which are the ants that you see walking around. Although the reproductive females are called “queens”, they have no power or political authority. One ant never directs the behaviour of another or tells it what to do. Ant colonies manage to collect food, build and maintain nests, rear the young, and deal with neighbouring colonies – all without a plan.

The collective behaviour of colonies is produced by a dynamical network of simple interactions among ants.  In most ant species, the ants can barely see. They operate mostly by smell. As an ant moves around it briefly contacts other ants with its antennae, or it may contact a short-lived patch of a volatile chemical recently left behind by another ant. Ants smell with their antennae, and when one ant touches another with its antennae, it assesses whether the other ant is a nestmate, and sometimes what task the other ant has been performing. The ant uses its recent experience of chemical interactions to decide what to do next. In the aggregate, these simple interactions create a constantly shifting network that regulates the behaviour of the colony.

The process that generates simple interactions from colony behavior is what computer scientists call a distributed algorithm. No single unit, such as an ant or a router in a data network, knows what all the others are doing and tells them what to do. Instead, interactions between each unit and its local connections add up to the desired outcome.

The distributed processes that regulate the collective behaviour of ants are tuned to environmental conditions. For example, harvester ants in the desert face high operating costs, and their behaviour is regulated by feedback that limits activity unless it is necessary. A colony must spend water to get water. The ants get water by metabolizing the fats in the seeds they eat. A forager out in the desert sun loses water while out searching for food. Colonies manage this tradeoff by a simple form of feedback. An outgoing forager does not leave the nest until it meets enough returning foragers with seeds. This makes sense because each forager searches until it finds food. Thus the more food is available, the more quickly they find it and return to the nest, stimulating more foragers to go out to search. When food is not available, foraging activity decreases. A long-term study of a population of colonies shows that the colonies that conserve water in dry conditions by staying inside are more successful in producing offspring colonies.

By contrast, another species called “turtle ants”, living in the trees of a tropical forest in Mexico, regulate their behaviour very differently. The turtle ants create a highway system of trails that links different nests and food sources. Operating costs are low because it is humid in the tropical forest, but competition from other species is high. These ants interact using trail pheromones, laying down a chemical trail everywhere they go. An ant tends to follow another and this simple interaction keeps the stream of ants going, except when it is deterred by encounters with other species. In conditions of low operating costs, interactions create feedback that makes ongoing activity the default state, and uses negative feedback to inhibit activity. Thus this is the opposite of the system for desert ants that require positive feedback to initiate activity.

What can we learn from ants about human society? Ants have been used throughout history as examples of obedience and industry. In Greek mythology, Zeus changes the ants of Thessaly into men, creating an army of soldiers, who would become famous as the Myrmidons ready to die for Achilles (from  myrmex – μύρμηξ – ant). In the Bible (Proverbs 4:4), we are told to “Look to the ant” who harvests grain in the summer to save for the winter. But ants are not acting out of obedience, and they are not especially industrious; in fact, many ants just hang around in the nest doing nothing.

Ants and humans are very different. Power and identity are crucial to human social behaviour, and absent in ants. Ants do not have relations with other ants as individuals. As an ant assesses its recent interactions with others, it does not matter whether it met ant number 522 or ant number 677.  Even more fundamental, an ant does not act in response to any assessment of what needs to be done.

However, we may be able to learn from ants about the behaviour of very large dynamical networks by focussing on the pattern or structure of interactions rather than the content. While we care about what our emails say, the ants care only about how often they get them. It is clear that many human social processes operate without central control. For instance, we see all around us the effects of climate change driven by many different social processes that are based on the use of fossil fuel. No central authority decided to pump carbon into the atmosphere, but the CO2 levels are the result of human activity.  Another obvious example is the internet, a huge dynamical network of local interactions in the form of email messages and visits to websites. The role of social media in the recent US election reflects how the gap between different networks can produce completely disparate views of what is happening and why.

The most useful insights may come from considering how the dynamics of distributed algorithms evolve in relation to changing conditions. The correspondences between the regulation of collective behaviour and the changing conditions in which it operates might provide insight, and even inspire thinking about policy, in human social systems.  For ants or neurons, the network has no content. Studying natural systems can show us how the rhythm of local interactions creates patterns in the behaviour and development of large groups, and how such feedback evolves in response to a changing world.

Useful links

The OECD organised a Workshop on Complexity and Policy, 29-30 September, OECD HQ, Paris, along with the European Commission and INET. Watch the webcast: 29/09 morning29/09 afternoon30/09 morning

Ants at Work: How an Insect Society is Organized Deborah M. Gordon

Ant Encounters: Interaction Networks and Colony Behavior (Primers in Complex Systems) Deborah M. Gordon

If the tortoise can do it, anyone can: greening household behaviour

Tortoises rushing about the Galapagos
Tortoises rushing about the Galapagos

Today’s post is by Naazia Ebrahim of the OECD Environment Directorate

Please join me in an ode to the giant tortoise, recently confirmed to be back from near extinction on the Galapagos Espanola Island after conservation work that began forty years ago. The population currently stands at over 1000, a spectacular recovery considering that only 15 remained in the late 1960s, when they were summarily rounded up and placed into a breeding program. There are now enough adults and juveniles surviving and repopulating to be self-sustaining.

Although one can never say ‘giant tortoise’ enough times, the island still requires some habitat restoration. The tortoises should be able to help that along, because in addition to being long-lived, they are also superb ecosystem engineers. They disperse seeds and other organisms, stimulate recruitment of cactus trees (one of their primary food sources) by distributing pods as they eat, and also, under the right conditions, control woody plant growth, which helps maintain habitat for an endangered albatross that also nests on the island. One could almost call them “masters of the (island) house”. Whoever thought this waddly wild wonk would be a model for humans to improve environment through adept household behaviour?

If society is Espanola Island – in need of some major restructuring to achieve ecological health – then the tortoises are the epitome of small, incremental change-makers that eventually create a paradigm shift. Their localised, small-scale influences – grazing on cacti and spreading seeds in their home range – eventually combine to shift the entire ecosystem towards its natural equilibrium.

But the tortoises could not, and cannot, do it all on their own. Sound like a familiar cry? The population decline was not simply due to natural causes: feral goats introduced in the late 1800s chewed their way through the island’s vegetation, destroying the cacti and causing an explosion of woody plants, which further inhibited cactus regrowth – a disastrous combination for the tortoises. (This is of course a prime example of the dangers of invasive species. The next time border control stops you in case there are fruit flies in your cut mango, don’t complain!) The breeding program thus had to be paired with a concerted goat eradication effort, which itself took around 20 years. Even with population viability, a good deal more effort needs to be put into removing woody plants before the tortoises can be fully effective as ecosystem engineers.

So, although the tortoises are powerfully influential in the aggregate, even they need a helping hand – or in other words, when the system has been flipped into a state unconducive to change, small-scale efforts can only take you so far. As found in a recent OECD study, greener household behaviour can combine to create major reductions in waste, as well as water and energy use. These actions may even form the vanguard of a wider societal transition, but these incremental moves are sometimes overpowered by larger structural failings. Moreover, evidence suggests that even when individuals are open to pro-environmental actions, including lifestyle sacrifices, they may not follow through due to societal pressures or perceived time, effort, and cost constraints – but they may accept political changes that will externally drive this behaviour.

Thus, for issues requiring large-scale reorganisation such as the energy or food supply systems, it is essential to create an enabling environment for society’s members to achieve their full potential. Taking a cue from Espanola Island, policy-makers may do well to foster top-down change, or barring that, to eradicate some of the “goats”. (No goats were harmed in the writing of this piece. The author would also like to clarify that she loves goats.)

Useful links

Greening household behaviour

OECD Environment Directorate on iSSUU, including Policy Highlights on water, food, transport, waste and energy


World Environment Day: Greening household behaviour

World Environment DayDo you suffer from Lord Henry Wotton syndrome? He’s the chap in Oscar Wilde’s Picture of Dorian Gray who said “To get back my youth I would do anything in the world, except take exercise, get up early, or be respectable”. It’s an attitude we all have to something or other we feel is desirable, but not to the point of making much of an effort. Saving the environment falls into that category for many people, but the good news for the planet is that the OECD has identified a group of people who “believe that sacrifices will be necessary to solve environmental problems”.

These “environmentally motivated” citizens form one of three groups identified in Greening Household Behaviour, based on the Environmental Policy and Individual Behaviour Change (EPIC) survey carried out in 2011 in 12,000 households in 11 OECD countries. The other two groups are the “environmental sceptics” who believe that environmental problems are exaggerated; and the “technological optimists” who believe that the problems are real, but that technological innovations are key to solving them.

You could divide the respondents in various other ways too, by age for example. In six of the eleven countries, older respondents were more likely to agree that their own generation bore significant responsibility for solving environmental problems, and that these problems should not be simply left for future generations.

Since the report is based on a survey, it’s interesting to try to spot differences between what people say they are prepared to do, and what they actually do (and what you do you yourself). Around 60% of respondents for example said they’d be willing to pay more for electricity generated from renewable sources for instance. One that intrigued me was the 45% of people who claimed they always washed clothes in cold water. Everybody I know is part of the 12% who answered “never” to that one, but I live in profligate Paris. How about you? Do you always, often, occasionally or never turn of equipment that has a stand-by function? Look at table 3.12 to see how you compare.

Apart from water and energy, the survey covers transport, waste generation, recycling, and food consumption, the theme of this year’s World Environment Day. The UN chose food to highlight the fact that while 1 in every 7 people in the world go to bed hungry and more than 20,000 children under the age of 5 will die today from hunger, 1.3 billion tonnes of food is wasted every year. This is equivalent to the same amount produced in the whole of sub-Saharan Africa.

We talked about this subject a few years ago on the blog, following the publication of a UK report that estimated that the average household threw away food and drink worth £40 ($65) per month, or around 15% of the shopping budget. Respondents to the Greening Household Behaviour survey report that approximately 10% of food is thrown away. There is a big difference from one country to another, ranging from 6% in France to 14% in Israel and 15% in Korea. Younger respondents report higher levels of food waste. Those concerned with natural resource depletion are less likely to throw food away.

They’re also more likely to buy organic, but here the cross-country differences are even more striking. Australians and Canadians aren’t really willing to pay much more for organic fruit and vegetables (a 5% price increase), while Koreans would accept a 23% hike. The reported willingness-to-pay for meat and poultry that takes animal welfare into account varies from 10% to 20%. Surprisingly (to me at least) the report says that “no significant pattern is found between income and expenditure […] for organic fruit and vegetables nor for meat and poultry labelled as taking animal welfare into account”.

Demand for electricity is another behaviour that doesn’t depend on income levels, but in this case the poor don’t have alternative choices. So without additional policy measures, they’re likely to suffer as a result of higher energy prices. Likewise, water conservation could be improved by according needs-based grants for water efficiency investments, or giving grants to tenants, who often don’t agree to pay to improve a home they don’t own.

How about this household? My colleague Liisa-Maija Harju has been looking at whether the OECD practices what it preaches regarding sustainable buildings, water use and waste management. To mark World Environment Day, OECD Secretary-General Angel Gurria has announced that the Organisation will be introducing a carbon pricing initiative based on an internal “carbon tax” on air travel of €20 per tonne to “reflect the cost of carbon emissions in OECD staff travel [and] encourage management and staff to give greater consideration to environmental aspects in making their travel decisions and arrangements”.

As Douglas Adams says in The Long Dark Tea-Time of the Soul: “It can hardly be a coincidence that no language on earth has ever produced the expression, ‘As pretty as an airport.”

Useful links

Serge Tomasi of OECD’s Development Co-operation Directorate on Putting green growth at the heart of development

OECD work on the environment

OECD work on green growth and sustainable development

The Race for the Green House

During the “space race”, as we called it back in the Atomic Age, US inventor Paul C. Fisher developed a pen with a gas-pressurised cartridge that he claimed could write in zero gravity. NASA bought them, while the Russians used pencils. A reminder that the best solutions don’t have to be high tech or complicated.

I thought about this on seeing Greening Household Behaviour: The Role of Public Policy, published today by the OECD. Years ago, a Swedish collective housing project was looking for ways to cut water heating bills. Everything failed, until somebody came up with the winner. Every household was given a free plastic basin for the washing up, and they stopped letting the hot water run when doing the dishes.

The OECD book suggests an even more obvious solution: charge people for what they use. Households charged for the volume of water used consume 20% less than those who aren’t charged. The book also says that charging by volume of garbage collected encourages people to generate less waste than charging by weight.

As well as water and waste, the authors surveyed 10,000 people across 10 OECD countries on energy use, transport, and organic food consumption.

And as well as demand-side instruments like charging, they looked at the impact of information and supply-side measures. The results suggest that money doesn’t explain everything, and behaviour can be influenced by a sense of civic duty.

There are wide variations by gender, income, education and other factors though. For instance, Mexicans and Koreans worry more about their environment than people in the Netherlands.  And many Australians and Norwegians say their own actions can make a difference.

In line with other surveys, respondents generally seem reluctant to pay more to use green energies like solar or wind, and household demand for environmental quality is unlikely to be enough to reach ambitious policy objectives.

Encouraging changes in the supply of greener energy, transport and other goods and services is one reason public policy has a role. Many of the proposed solutions would hit poorer people disproportionately, charging being the most obvious example, so any policy initiatives have to consider aspects other than the immediate goal as well.

This book is part of a longer exercise. The 2011 round of the OECD Household Survey will identify changes in people’s attitudes and behaviour towards the environment, and examine ways to promote green growth and the development of a low-carbon economy.

Useful links

OECD work on the environment

OECD work on green growth