Welcome to collective behaviour

We live in a world where phones are smart, mobs are dumb and Justin Timberlake is famous. If any of this strikes you as mysterious, you might have use for a steadily growing branch of science out there that aims to explain how all of it can be possible.

The study of collective behaviour concerns itself with how patterns of behaviour in groups of people (or for that matter, any animals, cells or particles) emerge from the individuals in that group and the interactions occurring between them. One wildebeest cannot know the trajectory of the herd across the plains, and yet a stampede of wildebeest moves as one, turning and changing direction together. From a distance, a group of starlings (known as a ‘murmuration’) moves so coherently that it can look almost like one animal rather than many, but no one bird acts as a leader, or organizes the other birds into formation. A termite mound is built from the combined efforts of thousands of tiny insects, dropping minute particles of soil on top of each other, yet the final product is achieved without any leadership or central organization of the work involved.

Understanding these patterns requires more than just an understanding of the individual animals. Can you predict the movement of a stampede just by looking at one wildebeest? The answer is probably no (unless you really have a way with wildebeest). But scientists studying collective behaviour have realized that if you can understand how wildebeest interact, then you do have a chance of predicting the movement of the stampede, even if you can’t predict the movement of an individual animal.

This relatively new approach to animal behaviour has its roots elsewhere – many of the methods and theories now being used to explain collective phenomena in biology were originally designed to explain the movement of particles and molecules in the apparently rather un-biological field of statistical mechanics. As scientists began to realize in the second half of the last century, many of the more complex problems in animal behaviour – particularly social behaviour – can be at least partly reduced to analogies of physical systems, many of which have already been studied in some detail.

A famous example of this analogizing can be found in one of nature’s most beautiful patterns, the synchronization of fireflies. How do some populations of fireflies synchronize their flashes so that hundreds of them flash in unison? Try thinking of each individual firefly, suggests mathematician Steven Strogatz, as a metronome. People have already studied how multiple metronomes, clicking at the same frequency on a shared surface, can synchronize their clicks even if they start out of sync. Through an effect called ‘coupling’ each metronome exerts a small influence on metronomes around it, such that slowly and almost imperceptibly, metronomes begin to synchronize their behaviour. The rules are simple, even though the pattern appears complicated to achieve.

That phenomenon, Strogatz argues, is analogous to the firefly phenomenon. Simply by slightly adjusting their flashing patterns according to the flashes of their nearest neighbours, individual fireflies contribute to the global synchronization of the whole group by using only simple rules. In a series of articles and later a whole book, Strogatz showed how many synchronized phenomena, from the coordination of cells in the heart to the orbit of the moon around the Earth can be explained using similar, not-as-complicated-as-you-think principles.

This blog is a continuation of that thought – that complex patterns do not require complex individual behaviour if there are interactions between individuals involved. Synchronization is just one of many phenomena addressed by collective behaviour; other topics include how information and opinions spread in social networks, how learning and memory are possible in the brain through interactions between neurons, and how organization in an ant colony might inspire the design of artificially intelligent systems.

The aim here is to keep an eye on the discoveries that bridge the gap between the individual and the pattern, the one and the masses. On the way, we’ll look at why some musicians are popular and others never sell an album (hint: it’s more than just talent), why governments are investing in the science of opinion spread, and why a telecom company resorted to studying collective behaviour in insects to maintain network coverage. Stay connected.

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