Can Random Noise Help Complex Systems? Raissa D’Souza Explains a Surprising Breakthrough
When researchers at Northwestern University discovered a way to prove that random noise can actually enhance the stability of collective behaviors — challenging the conventional understanding of noise as a destabilizing force — editors at Science turned to Raissa D’Souza, associate dean for research and professor of computer science and mechanical and aerospace engineering, at the University of California, Davis, College of Engineering, to help evaluate the significance of the work.
An expert in non-linear dynamics and network theory and a member of Science’s Board of Reviewing Editors, D’Souza reviewed the research and was invited by the journal to put the highly technical findings into a broader context. In the perspective below, published in Science, D’Souza explains the emerging concept of “disorder-promoted stability,” why the discovery matters for the field of complex systems and what its implications could be for science and society.
Fascinating collective behaviors arise when a large group of simple elements interact (1), such as the synchronized flashing of fireflies and flocking of birds. The prevailing theoretical expectation is that such behaviors are most stable when the individual elements are very similar (with near-identical parameters such as traits) (2, 3). This contrasts with many real-world examples (4, 5). Fireflies that act as noisy, irregular oscillators still flash synchronously in colonies. Electric power grids are intentionally designed with mixed power sources and mismatching response times to promote stability (3, 6). However, analyzing the stability of heterogeneous complex systems is challenging. On page 1241 of this issue Montanari et al. (7) report a new theory that shows how parameter heterogeneity and noise can promote stability. The findings establish theoretical underpinnings for when and why disorder is an asset for stability, opening new avenues for understanding and controlling collective behaviors.
The findings of Montanari et al. show that small amounts of disorder can be an asset to facilitate collective behaviors. Implications for the roles of noise and diversity in promoting stability span many domains, from human societies to homeostasis in biological systems. Engineering applications of such a theory include drone swarms, electric grids, and deep-learning algorithms. System disorder may prove to be a tool to enhance stability that nature exploits, and not a liability.
