Complexity to the Rescue

Physics Professor searches for answers to humanity's most intractable problems

If Neil Johnson were like others in his field, he might be studying quantum mechanics or condensed matter. But Johnson, a University of Miami physics professor who was recruited last fall from the University of Oxford, England, is no ordinary physicist. His research involves street gangs, guerilla wars, cancer tumors, and other nontraditional subjects – with one thing in common.

They exhibit “complexity,” which Johnson defines as “the phenomena that emerge from a collection of interacting objects.” “Physics has been very successful at studying individual particles,” he explained, “but now it’s beginning to turn its attention to the interaction of multiple objects when they’re all placed together.” Johnson, a practitioner of “complexity science,” is helping to lead the charge, which extends the reach of physics considerably.

For example, consider a bar in Coconut Grove. You and a few friends arrive there on a Friday night to find the place swarming with people, so you vow to return on Monday night, when the joint is likely to be less crowded. When Monday arrives, you are pleased to find that the scene is indeed relatively quiet. But you also overhear another group remarking how much more pleasant it is at the bar tonight. Several weeks pass and you notice the bar becoming increasingly crowded on Mondays, and pretty soon you show up on that day of the week and the place is packed. Your crew decides to move its get-togethers to Tuesdays. Surely the bar won’t be crowded on a Tuesday night….

Johnson uses this simple example to show that the outcome of an interaction depends on what the participants are doing, and on their memories and abilities to adapt their strategies based on history. While complexity science can be applied to virtually any scenario, Johnson is most interested in those that have practical applications.

In one of his projects, Johnson studies the complexity of conflicts. He has found that the war in Iraq, the war in Afghanistan, and the guerilla war in Colombia all show the same patterns of behavior. In fact, Johnson and his colleagues have found that all competitive scenarios, including armed conflicts, evolve in a similar manner and the outcome can be predicted mathematically. In the case of warfare, the outcome is the number of skirmishes that will result in a hundred, a thousand, or any number of casualties.

Johnson also works with a colleague at the University of California, Los Angeles, and the L.A. Police Department to model gang violence in Long Beach, California. He believes, unsurprisingly, that gang size is proportional to the amount of damage the group can do. Yet while large groups may be responsible for greater numbers of casualties, small groups are harder to control.

“It’s much easier to pick up a glass that’s intact than one that’s shattered into twenty thousand pieces,” said Johnson. “So what’s going to be easier to control – a few large groups or a thousand little groups that are individually weak but still wreak havoc because they’re all over the place?”

Armed conflicts, whether involving gangs, insurgents, or military units, aren’t the only skirmishes that Johnson studies. He also examines wars being waged within our bodies. The competition between cancer cells and normal cells, Johnson suggests, is not unlike what occurs between groups of people in a battle.

“Tumors are nourished by blood supply in the same way that a violent group is supplied with arms and other equipment,” he said.

Johnson and his postdoctoral researcher Charley Choe had previously collaborated with Cornell Medical School and Oxford University, but are now working with their new colleagues at the University of Miami’s Sylvester Cancer Center and Department of Mathematics on a model to predict the changes that must be made in the blood-supply system to confound cancer’s “logistics” and thus curtail the growth of a tumor. This work, the researchers hope, could some day have profound implications for treating – or preventing – the disease.

So does Johnson have a cure for cancer and a way to end war and gang violence? Not yet! If it were that easy, the problems wouldn’t be complex. But he does have an imaginative way to think about some of the most distressing phenomena facing humanity. He describes it at length in his 2007 book Two’s Company, Three is Complexity.