Diversity-induced resonance

One of the features characterizing robust systems is their adaptability to a change of the environment. We have put forward recently a mechanism, named diversity-induced resonance, by which the natural heterogeneity present in populations can induce a resonant effect: when those systems are subjected to an external varying weak forcing, their response is optimized for an intermediate value of the diversity. These findings, which are reminiscent of the stochastic-resonance phenomenon, show that intrinsic diversity might have a constructive role and suggest that natural systems might profit from their diversity in order to optimize the response to an external stimulus. Our results are sustained by general arguments as well as by numerical simulations of systems formed by diverse bistable and excitable systems. Those general ideas also find an application in the field of opinion formation. How do new ideas spread in a society? We argue that it is the diversity in the individual preferences that can trigger society changes induced by an external influence that would be completely inefficient for a homogenous society. We sustain this result by a numerical and analytical study of a particular opinion formation model in which opinions evolve by a mechanism of social pressure forced by an external message and weighted against some individual preference threshold. The microscopic mechanism is easy to understand: an external influence convinces first the individuals that were holding a contrary opinion but had an internal preference for the new idea. The mechanism of social pressure then allows this signal to propagate through a macroscopically significant proportion of the society. The idea that different sources of diversity can produce a resonant effect leads us to speculate that the amount of diversity present in some biological systems has an important function. Diversity could have been evolutionarily tuned in order to enhance the detection of weak signals. Whether natural systems have taken advantage or not from this diversity-related effect is a question that, as in the particular case of stochastic resonance, has not yet a clear answer.

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