Sunday, July 08, 2012

United With No Master

No, no, not mankind ... starlings !!

Jacques Callot

Amazing Starling Flocks Are Flying Avalanches

"In particle physics, synchronized orientation is found in systems with “low noise,” in which signals are transmitted without degrading. But low noise isn’t enough to produce synchronized speeds, which are found in critical systems. The researchers give the example of ferromagnetism, where particles in a magnet exhibit perfect interconnection at a precise, “critical” temperature.
“More analysis is necessary to prove this definitively, but our results suggest” that starling flocks are a critical system, said study co-author Irene Giardina, also a University of Rome physicist.
According to the researchers, the “most surprising and exotic feature” of the flocks was their near-instantaneous signal-processing speed. “How starlings achieve such a strong correlation remains a mystery to us,” they wrote."

Scale-free correlations in starling flocks

From bird flocks to fish schools, animal groups often seem to react to environmental perturbations as if of one mind. Most studies in collective animal behavior have aimed to understand how a globally ordered state may emerge from simple behavioral rules. Less effort has been devoted to understanding the origin of collective response, namely the way the group as a whole reacts to its environment. Yet, in the presence of strong predatory pressure on the group, collective response may yield a significant adaptive advantage. Here we suggest that collective response in animal groups may be achieved through scale-free behavioral correlations. By reconstructing the 3D position and velocity of individual birds in large flocks of starlings, we measured to what extent the velocity fluctuations of different birds are correlated to each other. We found that the range of such spatial correlation does not have a constant value, but it scales with the linear size of the flock. This result indicates that 

behavioral correlations are scale free

The change in the behavioral state of one animal affects and is affected by that of all other animals in the group, no matter how large the group is. Scale-free correlations provide each animal with an effective perception range much larger than the direct interindividual interaction range, thus enhancing global response to perturbations. Our results suggest that flocks behave as critical systems, poised to respond maximally to environmental perturbations.

Understanding  behavioral  patterns:  Why  bird  flocks  move  in  unison

Using a simple self-propelled particle (SPP) system, which sees the birds represented by particles with such parameters as position and velocity, the researchers from Budapest, Hungary, find that the collective switching from the flying to the landing state overrides the individual landing intentions of each bird.
In the absence of a decision making leader, the collective shift to land is heavily influenced by perturbations the individual birds are subject to, such as the birds' flying position within the flock. This can be compared to an avalanche of piled up sand, which would occur even for perfectly symmetric and cautiously placed grains, but in reality happens much sooner because of increasing, non-linear fluctuations.

"The behavior of the flock of starlings is different to the behavior of a group following a leader. Such a group would move in the same direction and would appear strongly ordered, but there would be no passing of information between individuals, and so, behavioral fluctuations are independent, with changes in direction of an animal other than the leader having little effect on other members of the group. The starlings’ behavior is an example of self-organization, and the collective response to events such as attack by predators gives them a distinct advantage."

Collège de Navarre
The College of Navarre was founded by Queen Jeanne de Navarre in 1305, who provided for three departments, the arts with 20 students, philosophy with 30 and theology with 20 students. Provision was made also for the scholars' support, 4 'Parisi-sous' weekly for the artists, 6 for the logicians and 8 for the theologians. These allowances were to continue until the graduates held benefices of the value respectively of 30, 40 and 60 'livres-tournois'. Entry could be allowed, without birth, family or age condition to every poor french citizen who would destined himself to the studying of grammar, logic or theology, medecine and law excluded.