Monday, May 24, 2010

Moffett & the Ants: Mode, Embedding & Emergent Complexity

Rather than read Mark Moffet, Adventures Among Ants, from beginning to end and only then write a review, I thought I’d post notes in the process of reading. Why? To see how it goes, that’s why.

As Moffett’s title tells us, the book’s about ants. I understand that ants are quite important in the world, and I have no problem understanding why someone would be fascinated by them, or, for that matter, by many other things as well. But I’m not myself fascinated by them.

I’m interested in human behavior and culture. So, what do ants have to tell us about ourselves? Moffett promises a lot on that score: the dust jacket copy talks of them “displaying behaviors strikingly like those of humans – yet on a different scale and at a faster tempo . . . warriors, builders, big-game hunters, and slave owners.” We’ll see.

Mode and the Reticular Formation

Let’s start with a passage on page 18:
Regardless of species, once an ant detects food, her searching behavior stops and is replaced by a series of very different harvesting activities: tracking, killing, dissecting, carrying and defending. In the majority of species, an ant can mobilize others to assist her. This communication practice is known as recruitment and usually involves chemical signals called pheromones. Often a wayfaring ant releases a scent from one of a battery of glands in her body, a mixture that serves to stimulate or guide her nestmates.
This reminds of Warren McCulloch’s concept of behavioral mode. The idea is that an animal must always be in one of several mutually exclusive modes of behavior. In a classic paper* McCulloch lists 15 different modes, including, for example, sleeping, eating, fighting, hunting and grooming. That seems roughly in the same ball park as Moffett’s list: searching, tracking, killing, dissecting, carrying, defending, and recruitment. Is ant behavior modal in the sense the McCulloch was arguing for vertebrate behavior? Perhaps.

McCulloch was specifically arguing about one of the most primitive structures in the vertebrate nervous system, the reticular formation, which is at the central core of the nervous system. The reticular formation has reciprocal connections with the rest of the brain, giving it a broad and pervasive influence on the global state of the nervous system. It’s that pervasive influence that McCulloch is thinking of as modal control. The ant’s nervous system is considerably smaller than that of even the most primitive vertebrate, so it’s not clear to me just how applicable McCulloch’s concept of control is, but . . . let’s not worry to much about that. Let’s just note the issue and press on.

Moffett tells us that ants use pheromones – bioactive chemical signals – to recruit the help of other ants to the cause. So reticular system uses biochemical signals to recruit the rest of the nervous system to a behavioral mode. It’s not just that neural transmission is electro-chemical in nature, but that specific neurotransmitters are keyed to specific behavioral modes and that those neurotransmitters are chemically the same as hormones that circulate through the blood system and are associated with specific behaviors.** Just as ants use chemical signals to recruit other ants, so the reticular formation uses chemicals to recruit the rest of the brain. Now consider the notion that the human brain is, in effect, 600,000 busy bees buzzing around inside the cranium. So, we have the reticular bees using pheromonal “trails” (“laid” in axons) to signal bees elsewhere in the brain.

Mere analogy? Perhaps. Let us continue on.

Complex Behavior by Simple Means: Simon’s Ant

Moffett goes on to explain how ants lay pheromonal trails through their environment. Thus “when ants form a line or travel in a column, they are tracking such a plume with their sensitive antennae.” These pheromones build up over time as more and more ants travel the trail. But when the food at the end of trail has been completely consumed “and the ants begin returning unrewarded, the pheromone is no longer replenished and the scent dissipates, attracting fewer ants.” This leads, Moffett argues, to “what appear to be deliberate choices by the colony, despite the ignorance of the individual ants of such matters as the size of the food item they are visiting and the number of workers needed to harvest it.”

Now we’re ready for one of the great metaphors of modern cognitive science, Simon’s ant (Google query). Herbert Simon opens his essay, “The Psychology of Thinking: Embedding Artifice in Nature,”*** in this way:
We watch an ant make his laborious way across a wind- and wave-molded beach. He moves ahead, angles to the right to ease his climb up a steep dunelet, detours around a pebble, stops for a moment to exchange information with a compatriot. Thus he makes his weaving, halting way back to his home. So as not to anthropomorphize about his purposes, I sketch the path on a piece of paper. It is a sequence of irregular, angular segments--not quite a random walk, for it has an underlying sense of direction, of aiming toward a goal.
After introducing a friend, to whom he shows the sketch and to whom he addresses a series of unanswered questions about the sketched path, Simon goes on to observe:
Viewed as a geometric figure, the ant’s path is irregular, complex, hard to describe. But its complexity is really a complexity in the surface of the beach, not a complexity in the ant. On that same beach another small creature with a home at the same place as the ant might well follow a very similar path.
That is to say, since the ant is living in a complex environment, its own behavior assumes that complexity by using relatively simple means to track that complexity.

Simon was thinking of a single ant. But single ants exist only in the imagination. Real ants live among their fellows, thousands upon thousands of them. And so the environment of a single ant is filled with other ants, giving us complexity upon complexity. Collectively, those ants remake their environment by laying down trails for one another, by consuming bits and piece of it, and by moving bits and pieces around to build their nests.

What’ve We Got So Far?

We’ve got simple creatures, ants, living collectively in a complex environment. They are modal creatures who signal one another with pheromones and who “map” their environment with pheromonal trails. They are thus deeply embedded in the environment. They live there, they track it, they transform it. Taken all together we have the emergence of complex behavior from simple “atomic” means – the nervous systems of ants.

In “The Busy Bee Brain” I played a conceptual game in which I took the bee as my atomic unit of behavioral activity and then asked you to imagine the human brain as consisting of 600,000 such units. Moffett is taking the art has his atomic unit and is going to build ant societies from it; that is to say, he’s going to develop concepts that will allow us to understand ant life. OK.

What happens when we take those concepts, whatever they are, and apply them to the human case, taking the individual human as our atomic unit? What will they tell us? I don’t think they’ll tell us very much about human culture, about such things as myths and stories, music, table manners, and so forth. But they well give us the “outer envelope” of human culture (cf. my remarks on Richerson's account of culture in my post on the phenomenological gut-check). If so, that would be valuable, for it will tell us that outer envelope can be generated by relatively simple means. What do we get from the complex means that humans do, in fact, have at their disposal?

More later.


* Kilmer, W. L., W. S. McCulloch, et al. (1969). "A Model of the Vertebrate Central Command System." International Journal of Man-Machine Studies 1: 279-309.

** cf. William L. Benzon and David G. Hays (1988). Principles and development of natural intelligence, Journal of Social and Biological Systems 11, 293 - 322.

*** Herbert Simon (1981). The Psychology of Thinking: Embedding Artifice in Nature, The Sciences of the Artificial, 2nd Edition. MIT press, pp. 63-98.

1 comment:

  1. Good idea here, book review on the fly.

    Perhaps because Moffett uses such whimsical pop-culture references in his footnotes, this quote:

    "McCulloch lists 15 different modes, including, for example, sleeping, eating, fighting, hunting and grooming."

    ...reminds me of the scene in Galaxy Quest where the Captain Kirk equivalent pauses mid-fight scene to fuss with his hair.

    Funny, but this suggests why.