There is a wide variety of collective synchronization phenomena in which a system composed by tens, hundreds or even thousands of elements suddenly locks to a common phase causing that the collective oscillates in unison. These phenomena have been observed since antiquity in the biological world through the behavior of plants and animals, for example, the migration of birds which are synchronized with the climatic cycles or the leaves of some plants species that are opened during the day and close at night. These observations continue to these days, such as: networks of pacemaker cells in the heart, circadian pacemaker cells in the suprachiasmatic nucleus of the brain, flashing fireflies, crickets that chirp in unison, etc. The synchronization phenomena may not only be found in biology, but in physics and engineering. There are also several examples of this "inanimate" synchronization, e.g.: two pendulums, arrays of lasers, microwave oscillators, superconducting Josephson junctions, etc.
Swarm intelligence was born from biological insights about the abilities of eusocial animal species, mainly social insects, to organize and adapt to the environment. It is based on the study of self-organized behaviors of these species. Self-organization is a set of dynamical mechanisms whereby structures appear at the global level of a system from interactions among its lower-level components, without being guide or managed by an outside source. Examples of self-organization in biology can be found in lichen growth, pigmentation pattern on shells, the flocking of birds or the fireflies synchronization.
Manuel Castillo-Cagigal, Eduardo Matallanas, Iñaki Navarro, Estefania Caamaño-Martin, Felix Monasterio-Huelin and Alvaro Gutierrez. Variable Threshold Algorithm for Division of Labor Analyzed as a Dynamical System, IEEE Transactions on Cybernetics, 44(12), pages 2242-2252, December 2014, ISSN: 2168-2267, IF: 3.781. doi: 10.1109/TCYB.2014.2305194.
Manuel Castillo-Cagigal, Arne Brutschy, Álvaro Gutiérrez and Mauro Birattari. Temporal Task Allocation In Periodic Environments: An Approach Based on Synchronization. Ninth International Conference on Swarm Intelligence, ANTS 2014 , September 2014, Springer International Publishing, pages 182-193. ISBN: 978-3-319-09951-4.
Manuel Castillo-Cagigal. A swarm intelligence approach based on coupled oscillators: an application in demand side management with photovoltaic distributed generation. Universidad Politécnica de Madrid. December 2014.