ALAN ALDA
Actor, Director; Author, Never Have Your Dog Stuffed: And Other Things I've Learned

The Edge of Fashion

About thirty years ago I started wondering how fads and fashions in ideas, behaviors, foods, clothes, medicine, politics, and pretty much every other human activity could seem to spread through a culture like a contagion. So I began collecting hundreds of papers and books from different fields in the hope of finding someone who was examining this deep and mysterious question in a way that was quantifiable. It's exciting to see Nicholas Christakis attacking this notion scientifically because we're at a point now generally where it's fashionable to talk about fashion but not necessarily to study it with rigor.  

The CEO, talking to his team of top managers says, "I want us to get in on the ground floor of the next bandwagon." If this recent New Yorker cartoon brings a smile to our face it's because we realize how difficult, if not impossible, it is to guess which gaggle of people will become the next parade. On the other hand, our smile may be checked in mid grin by the thought that there are actually CEOs all over the world trying to do exactly that: catch a wave that will carry them to the Promised Land. The small industry of guerilla marketing offers hope of getting there, but more like preachers and fortune tellers; more like explorers on a random walk than travelers with a map.

The problem that Christakis is facing head on, I think, is that this is a complex problem with interlocking complexities within it, each containing more complexities, like an inscrutable Russian doll.

It's hard enough to get increasing numbers of semiconductors on a computer chip to communicate in the best possible way, but it's even harder to understand how people communicate because we're not simple on-off switches. We're not merely units in a swarm; we're, each of us, collections of swarms — from the cells in our hearts to the neurons in our brains.   

It seems to me that figuring out how these collections of swarms influence one another is going to require researchers from many different fields to become interested in this question. In a lab I visited while interviewing scientists for Scientific American Frontiers, I saw a petri dish full of heart cells that were pulsing in unison. I wondered what signals were they sending and receiving that triggered this synchrony. The flocking of birds can be modeled on a computer with the simple rule of not getting too close, or too far, from a neighbor, and yet a giant flock of birds will apparently turn as one. So are they responding to a signal from a neighbor or to a signal from a mini-swarm within their flock that has reached a critical mass and serves as a super signal? Or both? Can the people who study the flocking of birds and those who study the pulsing of heart cells help us understand the signal/response interactions of even more complex systems, like networks of people?

For instance, Christakis mentions the remarkable study in which obesity seems to be contagious within a circle of friends. It reminded me of my interview with Jeffrey Friedman who discovered leptin, the hormone that signals how much fat is in the body. He painted a picture for me of how all kinds of cues (smells, thoughts, behaviors, and more) can trigger a complex interaction among leptin and other hormones within us that in turn give us the powerful sensation, even though we're full, that we're actually starving. If I don't have this piece of pie, I could die. Is our intricate hormonal system responding to signals from the even larger system of the circle of our friends? I'd love to hear a conversation between Christakis and Friedman.

The edge of the network that makes up the scientific community could make an important breakthrough if it started interacting on this question.

Maybe Edge could become a super signal on that edge.

NICHOLAS A. CHRISTAKIS
Physician and social scientist, Harvard

In his comments regarding "Social Networks Are Like the Eye," Alan Alda highlights three distinct, albeit inter-related issues, two of which are also touched on by Douglas Rushkoff: the role of mechanisms of spread in social networks; the problem of determining the mechanisms of spread; and the analogy of a swarm that is sometimes used to understand certain social network processes.

In our ongoing research program, James Fowler and I are keenly interested in mechanisms, but we regard them as a latter step in a process of understanding social networks.  In our paper on the spread of obesity, we consider two mechanisms by which something might spread from one person to another socially: one person might copy the behaviors of another, or one person might adopt the ideas or norms of another. But our thinking about these possibilities remained necessarily speculative given the limitations in our data in that study. However, Alda’s comments force another thought: even if one were to empirically document that a norm spreads from person to person, and that this was, in fact, the mechanism for the spread of, say, obesity, this observation might merely push the problem back a step, because then another question might be begged: what is the mechanism by which norms themselves in turn spread?  An infinite regress (sometimes known as scientific inquiry) might then start, with ever-finer levels of reality being probed. The irony here is that the whole effort to understand social networks indeed is mainly about heading in the other direction, towards ever-larger levels of reality!  Understanding how smaller bits are assembled into larger structures, rather than unpacking larger structures into their smaller constituents is our first objective in understanding social networks.

That is, for Fowler and myself, the first challenge is to understand the rules by which social networks form (their structure); the second challenge is to understand what they do (their function); and the third challenge is to understand how they do it (the mechanism). The intellectual and empirical problem, alas, in the case of social (as compared to physical or biological) networks is that all three of these are inter-connected and there may be particularly complex feedback loops among these levels.

As Alda and Rushkoff suggest, the actual mechanism of contagion in behaviors is thus both fascinating and difficult to fully understand. Why, exactly, do I copy you?  And how?  There are a variety of biological, psychological, and sociological reasons, of course, and they each might operate a different empirical and ontological levels.  But to nail them down, and to demonstrate their operation in hyper-dyadic circumstances, is another matter.  We can provide two illustrations of possible mechanisms — one social and one biological, as follows: 

I, and others too, might copy you because, in seeing you do something in particular (eat, clean your gutters, listen to Mozart), you provide a demonstration of what I could do and how I could do it.  What flows through the air between you and me (and hence across our ethereal, social network tie) is the sight of you doing something, and this provides learning to me (a demonstration effect) that allows me to do something I might not previously have been able, or wanted, or thought, to do.  Of course, this does not deal with my motivation!  Just because I see you do something does not in and of itself mean that I will necessarily want to copy you (nor, frankly, that I should copy you — for example, if you get depressed or if you commit murder, I should probably not copy you — although, even with these two phenomena, there is evidence that people actually do copy others, even others who are quite far from them in the social network and not directly tied to them). Of course, there is good evidence that we primates simply innately like to copy others (to try things out, as it were), and this learning-by-copying, this curiosity, and the social integration that results from this copying almost certainly all served an evolutionary purpose.  Nevertheless, the question remains: are our desires endogenous, exogenous, or both?  Both, of course.  But it is not easy to sort out.  

Now, a different reason I might copy you is that there is something biological going on. For example, one person doing something may signal others to do the same (think of human pheremones, or menstrual synchrony among female roommates). Or, inhaling the second hand smoke of another person might contribute to our own addiction to tobacco. Even the leptin pathway might be involved, as Alda suggests, as a neurohormonal mechanism of the contagion of obesity ('without this pie, I could die,' indeed.) 

Finally, there is the issue of the swarm metaphor that both Alda and Rushkoff, in different ways, evoke.  This metaphor is both appealing and apt, and it is related to the notion of a "super-organism" mentioned in my original Edge interview. Like other investigators, Fowler and I have no doubt that human societies do, at least at times, evince swarm-like properties.  However, as Alda suggests, a swarm of ants or bees or birds or fish might actually be closer to the synchronous beating of heart cells than to the behavior of people.  A riot is a kind of human swarm. But the more sustained social networks in which we are all embedded (i.e., the kind of social organization that is both less ephemeral than a riot and more complex in terms of the ties between the actors) exhibit properties that hives and swarms do not; and the reason for this is that humans are conscious of their social network embeddedness (and conscious of much else too).  So, the kind of emergent properties seen in ant hills or bee hives might actually better resemble those seen in networks of inanimate objects (such as networks of power stations or computers) or networks of non-sentient items (like heart cells) than they resemble networks of humans.  Nevertheless, some of the phenomena seen in human societies (like riots, and also like markets) might indeed be just like swarms.

Hence, in some aspects of our lives, no doubt, we may indeed resemble ants, simply following the person in front of us. And this in turn does raise the concerning possible link to an individuality-crushing, soul-effacing "tyranny of the masses" that Rushkoff notes. Of course, even here, we should not set up false dichotomies: for people may have both an individual and a collective existence, be both disconnected and connected. Since it is hard to believe that we are connected for no reason, I myself am of the view that social networks, and our embeddedness in them, serve a valuable and — I will go out on a limb — good purpose.