Creative Generalist Q&A: Dirk Brockmann
Dr. Dirk Brockmann is Associate Professor for Complexity at Northwestern's Department of Engineering Sciences and Applied Mathematics and a theoretical physicist at the Max-Planck Institute for Dynamics and Self-Organization in Göttingen, Germany where he leads a team of young scientists. His research focus is on complex dynamical phenomena in physics biology, sociology, neuroscience and economics.
Dirk is convinced that many of the hardest problems we face today sit at the boundaries of conventional disciplines. In the past years, Dirk has investigated systems as diverse as transport phenomena in living cells, dynamics of neural networks and human eye-movements. Recently he became interested in the spread of human infectious diseases such as SARS, HIV/AIDS and pandemic influenza. Since then, Dirk has made valuable contributions to the understanding of disease dynamics in a globalized world. In 2004, he published the first model that was able to describe the global spread of SARS in 2003, taking into account the entire international flight traffic network. Shortly thereafter he discovered fundamental mathematical rules that underlie human travel behaviour by analyzing the geographic circulation of over a million individual dollar bills in the United States. This data was collected at the online bill tracking game www.wheresgeorge.com.
Dirk, could you please explain generally what you learned by connecting the study of epidemics and pandemics with money circulation?
The key piece of information we gained in the study is that human travel behaviour follows simple mathematical laws on a wide range of scales. For example, the probability of traveling a certain distance in a short period of time, say a few days, follows an inverse power law. That means: trips of larger distance are less likely to occur than those of short distance. While this is intuitively clear, it is surprising that this can be described by a simple mathematical law. We can now attach actual numbers to this behaviour.
With regards to infectious diseases, would you say that humans are perhaps too closely interconnected and too mobile?
In a way, the answer to this question is yes. In the course to development of human civilization two factors really support the emergence and endemic state of human infectious disease. Endemic means that diseases come and stay. One of these factors is the population density. Most of the diseases that exist today have not been around for too long and their existence is connected to the fact that cities and urban structures emerged. The other factor is how cities and places with a high population densities are coupled by means of individuals' travel between them and can transmit disease from one place to the next. The intensity of modern human travel really breaks down the boundaries between connected places and everything becomes a huge population in which emergent diseases can persist even more easily.
It was your cabinetmaker friend Dennis Derryberry who tipped you off to Hank Eskin's Where's George?! website. How significant was that non-specialist input to your research? How so?
In my own personal experience as a scientist, the interaction with non-professionals is crucial. And this is quite generally so. Once you've become a specialist (which I try not to) there is the danger of developing a skewed and twisted viewpoint on the things you do research on. Therefore it is vital to communicate with "normal" human beings in order to re-adjust your view on matters. In this specific case, Dennis Derryberry's role was vital. When I visited him after a physics conference
in Montreal, he asked me what I was interested in and I said human travel. He then mentioned wheresgeorge.com. So it was his intellectual wit that actually made the connection between money dispersal and human traffic.
At Idea Festival, you remarked that "the viewpoint determines the question." What did you mean by that?
The way we look at stuff is largely determined by our experience, our interest, and our profession. For example, if I like cars and see a Ferrari I may ask myself how fast does it go. If I'm an engineer who works on the construction of cars I may ask what kind of engine does the car have? In science that's basically the same. Scientist's views are biased by their interest. If I look at two types of trees, for example a birch and an oak tree, I may ask what are the differences between the two, what makes them unique (the biologist view) or I may ask what do these two systems have in common (the physics approach). Neither one is better than the other; they go hand in hand.
In your view, what is complexity? What is complex dynamical phenomena?
Ha. This is difficult. I think "complex" is best understood in comparison with "complicated". Complicated things are difficult to grasp. Complex systems are those that exhibit behaviour that looks complicated but is governed by rules that are often not complicated. So, complex dynamical phenomena are those that can generate a rich dynamical behaviour but that are generated from simple rules.
What is the value of inter/multi-disciplinary study?
In connecting viewpoints. That's often difficult because people are frequently reluctant to look through the other person's eyes.
What would you say are some of the key things necessary for successful cross-disciplinary work? What are the challenges?
Open-mindedness. Willingness to give up or change individual viewpoints. Lack of arrogance and vanity.
Can you share with us any details about what projects you're currently pursuing?
Currently I'm still working on human travel, this time from a network perspective. I'm also shifting my focus on social networks and social dynamics. I'm also interested in the emergence of hierarchies and stability of social networks.
Finally, where do you look for inspiration? Are there any organizations, people, books or websites that you find especially inspiring?
I don't actually look for inspiration. Ideas, as important they are for science, can not be generated at will. The only thing one can do is to work on the setting in which one can develop ideas. I mentioned above that I talk to non-specialists a lot. Almost all my friends are non-scientist and some of them are much smarter than some of my professional colleagues. Most of my ideas come at random and very few of them when I'm at work.
Thanks, Dirk.