Be it through the Internet, Facebook, the local grapevine or the spread of disease, interaction networks influence nearly every part of our lives.
Scientists previously assumed that interaction networks without central control, known as self-directed networks, have universal properties that make them efficient at spreading information. Just think of the local grapevine: Let something slip, and it seems like no time at all before nearly everyone knows.
By observing interactions in ant colonies, University of Arizona researcher Anna Dornhaus and doctoral candidate Benjamin Blonder have uncovered new evidence that challenges the assumption that all interaction networks have the same properties that maximize their efficiency. The National Science Foundation-funded study was published in the Public Library of Science on May 20.
"Many people who have studied interaction networks in the past have found them to be very efficient at transferring resources," said Blonder. "The dominant paradigm has been that most self-organized networks tend to have this universal structure and that one should look for this structure and make predictions based on this structure. Our study challenges that and demonstrates that there are some interaction networks that don't have these properties yet are still clearly functional."
"There are a huge number of systems that are comprised of interacting parts, and we really don't have a good sense of how these systems are organized," said Blonder. "Think of a city with many people or the Internet with many computers. You have all these parts doing their own thing and somehow achieving some greater function."
The researchers chose to use ant colonies as models for self-directed networks because they are comprised of many individual components - the ants - with no apparent central organization and yet are able to function as a colony.
"We think no individual ant has a sense of purpose," said Blonder. "It doesn't go out one day and say: 'I'm going to move this pebble for the greater good of the society.' It has a behavioral program where if it sees a pebble, then it's likely to move it. The reason that contributes to the good of the colony is an evolutionary argument where the ants' behavior is shaped over thousands or millions of generations."