I’ve found the buzzword I’ve been looking for. I’ve also found the people who have been doing research in my area, and they are all in Northern Europe. I wonder if it’s too late to move to Sweeden.
The term ‘stigmergy’ was created by Grasse in the late 50’s, from the Greek stigmos meaning ‘pricking’ and ergon, meaning ‘work’. He was studying ant and termite behavior, and ran headlong into the so-called “coordination paradox”
The concept of stigmergy provided an alternative theory for understanding the coordination paradox, i.e., the connection between the individual and the societal level: looking at the behaviour of a group of social insects,they seem to be cooperating in an organised, coordinated way, but looking at each individual, they seem to be working as if they were alone and not involved in any collective behaviour.
Grasse was looking for “a class of mechanisms that mediate animal-animal interactions”, which was severely lacking from the scientific repertoire. The only tool available were analogies drawn to the functioning of an organism in terms of its individual organ systems, but this had no explanatory value, and in fact suffered from the same coordination issues. The alternative was to merely describe the individual agents with no respect to their interactions. This view was advocated by Rabaud, who was generally skeptical of holistic explanations.
The focus on individual behaviour had a tendency of oversimplifying the nature of social phenomena, and Rabaud claimed that the only cause of behaviour lies within an individual, and “if cooperation occurs it is only by chance and as a result of unexpected incidents” (Theraulaz & Bonabeau, p. 99). According to Rabaud each individual was doing its own work, without paying any attention to the work of others, and therefore they had no noticeable influence on each other. Rabaud considered collective work as merely a “juxtaposition of individual works”, and that “common work is no more than a side effect of interattraction that gather individuals together” (ibid., p. 100).
However bad this view turns out for the human case, it was even worse for the apparently more simple case of ant and termite colonies. However, Rabaud’s work was not entirely unhelpful, and in typical 50’s behaviorist fashion his work relied on the central notion of interaction.
However, the work of Rabaud led to the introduction of two important concepts: interaction and interattraction. Interaction is the reciprocal action where one individual’s action may influence and modify the behaviour of another individual. The term of interaction formed a bridge between the individual and the social level. Interattraction means that animals belonging to a social species are attracted in a specific way by other animals belonging to the same species. These ideas were further developed by Grasse, whose basic idea was that “sociality is not a trivial consequence that results from interattraction, but a biological characteristic deeply rooted in the ethological heritage of every species” (ibid., p. 101). The action of an individual can provide a stimulus for other individuals, who respond with another action, triggered by the previous action. In termite nest building, for example, the existence of an initial deposit of soil pellets stimulates workers to accumulate more material through a positive feedback mechanism, and each worker in turn creates new stimuli as a response to the stimulating structure. This allows complex structures, such as pillars and arches, to emerge without central coordination. Thus each individual, or the result of its work, can act as a direct source of stimuli for other individuals. In addition, this mechanism allows for an indirect coordination of individual activities as each individual’s activities organise the environment “in such a way that stimulating structures are created; these structures can in turn direct and trigger a specific action from any other individual from the same species that comes into contact with them. Chemical trails that are produced by some ants species…, muleteer trail networks, and even dirt tracks and trail systems in man… result from interactions of this kind” (p. 102).
The mediating mechanism for social interaction, then, was not to be found in the individual but in the environment itself that is structured by the individual participants for group coordination. This view of ant behavior has become the standard view, but the source of this view is often under appreciated. In this way we solve the coordination paradox, through indirect communication.
The basic principle in stigmergy states that traces left and modifications made by individuals in their environment may feed back on them and others: activities are partly recorded in the physical environment, and this record is used to organise collective behaviour. As the examples show, various kinds of storage are used: chemical traces, building material, spatial distribution of elements, etc. Thus individuals do interact to achieve coordination at the societal level, but they interact through indirect communication, and therefore, looking at each individual, they do not seem to be engaged in coordinated, collective behaviour. In sum, stigmergic explanations of social insect behaviour consider the agents as simple creatures, simple in the sense that without deliberation they (re-) act or respond according to stimuli provided by other individuals and/or the environment.
I found this while looking through the evolutionary robotics literature for information on the distinction between proximal and distal explanations of functional organization. The paper I cite is by Susi & Ziemke (2001) entitled “Social Cognition, Artefacts, and Stigmergy” (PDF). More information can be found on this disappointingly low-tech website on stimergic systems, which references everything from Lingo to Google’s patent.
‘Stigmergy’ is an ugly, awful word. It doesn’t roll off the tongue, it must be scraped forcefully. But the concept itself is exactly what I have been looking for. I am now opening discussion for any suggestions on what would be a better term.
I don’t know it seems there is still an issue with outside observation. I would say that some of the conclusions about individual behavior versus societal interaction need to factor in the observer that makes these qualifications. In this sense I’d have to say that there is like a Heisenberg uncertainty principle at play here in the act of observing the ants. Relying on how things “seem,” I don’t know if this “coordination paradox” is correct in the first place.
Are you seriously implying that ants don’t work as a collective unit? I don’t understand what biases you think observation has on the results here. The only points here is that the colony functions as a collective unit and that there is no centralized control over the individual members of the colony. Thats the paradox. It has nothing to do with observational bias.
No I am not implying that ants don’t work as a collective that is quite obvious. I take issue with this part: ” …looking at each individual, they seem to be working as if they were alone and not involved in any collective behaviour.” I guess that is where the paradox comes in? I just don’t know how they can qualify the individual behaviour in such a way if the conclusion from the observations is that ants do function as a collective unit.
I’m still confused. Are you denying that ants are individual organisms? You can do that, I suppose, but it seems rather implausible. Most ants are clones, but they are each born from separate eggs and have their own histories. The paradox comes in by seeing ants as individual organisms who work as a collective, and there is no central control for the behavior of the group. The question is where that centralized control comes from, and the answer Grasse gives is through the environmental artifacts manipulated by the individuals. The coordinated behavior of ants is explained in terms of the pheremone trails they leave on the ground, etc.
They aren’t concluding that ants work as a collective, it is part of the data that needs to be explained.
Quit with the Straw Man thing here. I am curious about the real issue of what makes something a collective? I would think it is defined simply by the Utilitarian nature of the results. I do not see where this ellusive “central control” comes in? What is an example of a central control in other collective systems?
There is no central control, unlike in organisms that have central nervous systems regulating behavior. Ant colonies have no central regulation. So the idea is that what makes the colony a collective is that there are common environmental resources which the individuals draw on to organize group behavior. The point is that the control mechanisms aren’t stored in any individual member of the colony, but in the resources of the chared environment. The structure of the termite next informs the individual workers about which structures to build, and where. The result is organized activity with no central locus of control.
What makes this interesting to me is that we typically think of computer systems as merely aspects of the environment that function purely as the sorts of environmental resources that facilitate human-human interaction. But it seems apparently obvious to me that machines are not merely passive resources in the environment, but active contributors to the kinds and contents of the interactions we engage in. And therefore, that the appropriate sense of ‘collective’ in the human case will consider both human and machines as members of that community.
So, where does instinct end “stigmergy” begin? I could roll a ball of mud and deposit it, but my fellow humans aren’t going to naturally desire to deposit their ball of mud next to mine, resulting in the creation of arches and and whatnot.
Or to approach it from another angle, there are certain commonalities to ant hills, which is why we have a term for them: “ant hills.” Those hills would not spontaneously arise, so the commonality of the structures must come from a central plan of sorts, and I suppose that we agree that this “central regulation” is embedded, in the form of instinct, in each (or in most) of the ants’ brains. They don’t have to imagine the result, of course, but they exhibit that behavior for an evolutionarily determined purpose.
I have no problem with “sigmergy” as a method of communication, but the environment itself is simply a medium for communication, and the blueprint continues to be instinctive.
I guess I don’t get what the “paradox” is, regarding collective ant action.
Surely you don’t think that when an ant finds food and tells the others where that food is, that the whole process is genetically determined? The information the ants communicate depends essentially on the environment, and the communication itself is stored in the environment, allowing the individual ants to be relatively ‘dumb’ units and yet display complex organized behavior.
All the genetic ‘instinct’ gives the ant are its basic communicative resources, (the ability to produce pheremones and to translate the pheremones of others to inform their behavior), and a sensitivity to the kind of interaction that occurs between members of the species. Otherwise, the whole thing is stored in the stigmergistic (oh god I hate that word) environment.
Look, the termite’s genes don’t tell it to built an arch here or a pillar there. Where it builds an arch depends on the environment and the actions of others. All it knows is that if some members of the community do something, to respond in some particular way. The end result gives you complex arches and pillars, and maze-like ant hills, but no individual has the blueprints for those structures built into their genes.
I don’t think about this stuff as much as I used to, so forgive me if this is complete wankery, but…
Consider a relatively non-social animal, such as a bird. A bird builds a nest using items from the environment. The bird will pick items from the environment and choose where in the environment to build. Why does the bird always pick a spot up in a tree rather than on the base of the tree or out in the open? It’s either reason or instinct, and I bet on instinct.
Back to the insects. you write:
“All it knows is that if some members of the community do something, to respond in some particular way. The end result gives you complex arches and pillars, and maze-like ant hills, but no individual has the blueprints for those structures built into their genes.”
The key phrase here is “respond in some particular way.” This is the instinct, and this is where the blueprint is, in effect, stored. No, the termite doesn’t have a picture of the pillar or any plan beyond “responding in a particular way.” But that response has been honed over the course of termite evolution so that, when termites respond in a particular way, the results are the pillars or other structures that help termites survive.
I think we are saying the same thing using different vocabulary, but my point is that the fact that insects communicate using the environment is interesting, but I don’t see what “paradox” it solves.
Hey, one other thing. The creation of hills in the oldest settlements on the edge of the North Sea might just be an example of humans behaving stigmergistically. I’m not confident of the history, but I think there’s evidence that humans just keep adding soil to their hills without necessarily communicating about a master plan. Observing the enviroment, and improving it, so it can be observed by the next group, and improved.
I think we are basically on the same page. I have to remind myself that these problems and solutions are really a product of the behaviorism of the 50s, and to a large extent people have switched vocabularies and organizing frameworks.
My only point was that we have to be careful about what we attribute to ‘instinct’. The instinct to ‘put mud where others put mud’ isn’t the same thing as in instinct to build pillars, even though that is the end result. The pillars aren’t in the individual, they only exist as a product of the combined contributions of the community members.
In any case, here is another example of stigmergy in action.