How do people decide when to stop clapping after a performance? Why was the mobile phone adopted quickly and universally after its emergence? Why did the birth rate in Europe suddenly plummet in the late 20th century?
The common element is an environment where people are susceptible to the influence of others. According to a recent report in the international science news weekly New Scientist, two French physicists—Quentin Michard, of the School of Industrial Physics and Chemistry in Paris, and Jean-Philippe Bouchard, of the French Atomic Energy Commission—who were seeking a model for such imitative behaviour found what they were looking for close to home. The progress of fads and fashions—in thought, opinion or consumer behaviour—can be described by one of the laws of magnetism.
It makes sense, when you think about it. Magnetism depends on the behaviour of individual atoms. It occurs when atoms align the direction of their spin. An overall applied magnetic field—from another magnet or an electric coil—coerces the spin of individual atoms in magnetic material to point in a particular direction, but the atoms are also influenced by their neighbours. In other words, the more atoms pointing in one direction, the greater the push for the others to go along.
Now, if you substitute people for atoms, and behaviour for spin, you have a description of imitative behaviour. When Michard and Bouchard checked the predictions of this model against what happened with mobile phones, birth rates and clapping, they found these behaviours conformed to the mathematical pattern established by the law of magnetism. Their model suggests that the rate of change of behaviour accelerates in a mathematically predictable way, and that the speed with which an opinion or technology is adopted depends on how strongly people influence each other.
It started Archimedes thinking about other imitative behaviours—particularly those relating to seemingly intractable problems, such as dealing with climate change and promoting ecologically sustainable lifestyles, or resolving conflicts such as the turmoil in the Middle East.
If Michard and Bouchard are right, their model supports the idea that small, but significant, public acts of responsibility can be highly influential. Just as the dying away of applause at a concert begins with a few people deciding enough is enough, so the revolution demanded by climate change needs more people to take small decisions which can influence their neighbours.
No one seriously thinks ratifying the Kyoto Agreement will solve the problem of greenhouse