Rhythmic activity patterns can be observed in many natural phenomena. Some examples are: Oceanic waves and tides; plants growth; activity in beehives and, probably, some types of human activities.
According to B. COLE, "… isolated individuals and individuals in sparsely populated groups have a pattern of activity-inactivity that is described as deterministic chaos. This is not a random pattern, but one which is so complex that it is impossible for an observer to predict what a particular ant will do next" (in B. GOODWIN, 1998)
Such complexity must depend on the interactions among individuals, which become reciprocally constraining, but with considerable leeway due to their scattering and the differential delays in their reciprocal perception.
GOODWIN and colleagues did modelize ants behavior through a neural network of cellular automata (p.34).
They observed that the output of the network was chaotic. Moreover, "increased density of individuals increases the amount of activity by individual, simply because of the higher frequency of stimulation between individuals…
So model ants, behaving chaotically and interacting 'socially' by stimulation, can generate a collective rhythm through a colony. This is a clear example of emergent behavior… " (p.34) And "… the model showed that there is in fact a wide range over which the sensitivity can vary and still produce collective rhythms. This suggests that rhythmic activity patterns are robust consequences of colonial living. They may in fact be hard to avoid. Collective rhythms is an emergent property that has been described as "order for free" (p.34).
This could be usefully compared with the inset and development of the "social phase" in Dictyostelium discoideum, and is probably significant in numerous other gregarization phenomena.
GOODWIN adds: "There is another important property of colonial rhythms that the model revealed. Rhythmic activity emerges suddenly above a critical density. But what type of discontinuity are we dealing with? The model showed that it has the characteristics of what physicists call a phase transition: a sudden change of state from one type of order to another… At the critical density, what was a collection of individuals doing their own local thing begins to change as global order emerges via activation waves that propagate through the entire colony" (p.35)