A general concept has been developed over the decades about the importance of interactions between congeners which tend to cluster into large groups, forming a kind of ‘superorganism‘ consisting of individual ‘agents‘, for defence, predation, or adaptation to the environment.
In the absence of a centralised control structure, such collections of agents follow very simple rules dictating how individuals in the group should behave. While following only local interactions, an apparently ‘intelligent’ global behaviour of the group, unrelated to that of individual agents, may emerge. This collective group behaviour is often termed ‘swarm behaviour‘ or ‘swarm intelligence’.
Some of these interactions can be described via models of ‘cellular automata’ responsible for self-organised collective behaviour. The idea developed by John Horton Conway and published as ‘The Game of Life’ showed how simple rules of interaction between geometrical shapes can generate novel structures simulating autonomous behaviour.
Examples of swarm behaviour include ant colonies, bee colonies, fireflies, fish schooling, bird flocking, hawks hunting, animal herding, and microbial growth.
At night in certain parts of southeast Asia, thousands of male fireflies congregate in trees and flash in synchrony. Recalling displays he had seen in Thailand, Smith (1935) wrote1: “Imagine a tree thirty-five to forty feet high…, apparently with a firefly on every leaf and all the fireflies flashing in perfect unison at the rate of about three times in two seconds, the tree being in complete darkness between flashes Imagine a tenth of a mile of river front with an unbroken line of [mangrove] trees with fireflies on every leaf flashing in synchronism, the insects on the trees at the ends of the line acting in perfect unison with those between. Then, if one’s imagination is sufficiently vivid, he may form some conception of this amazing spectacle.” The mechanisms underlying this degree of synchronisation are still being investigated.2
Experimental studies demonstrated that the coupling in fish schooling occurs via visual inputs and activation of the mechanical sensors of the lateral line. These sensory inputs operate together to set limits on the spacing between individual fish as the school moves through the water column: the lateral line detects when the fish are too close together, while visual cues are used to track neighbouring fish3.
The flocking of the most common birds in the skies of Rome, starlings (Sturnus vulgaris) has been well studied. Investigators from La Sapienza University in Rome led by the Nobelist Giorgio Parisi,4 found that by reconstructing the 3D position and velocity of individual birds in large flocks of starlings, they could determine the extent to which velocity fluctuations of different birds are correlated with each other. They 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.” Their results suggest that flocks behave as critical systems, poised to respond maximally to environmental perturbations.
The longer term evolutionary value of actions is correlated with their relevance in supporting survival. On one hand, they may be associated with pleasure, or, on the other, with adverse conditions of survival generating an unpleasant sense of danger and fear. These experiences correspond to affective states including emotions, moods, sentiments, feelings, etc. Such affective states occur at all levels of the internal neural loops, from a simple escape reaction mediated by spinal cord circuits to higher circuits involving long term associating or avoidance behaviour in complex social conditions.
A most important coupling between individual is the one that ensures the continuity of the species. Sexual reproduction represents a powerful coupling between individuals and underlies kinship relations within families as well as more extended social groups. Strong family or kin bonding helps survival of young in many non-human societies such as most species of birds and mammals. Such coupling mechanisms in humans are described as attachments, between parents and children, between and within broader kinship, tribal and larger social groups.
Interaction between humans is the very essence of human societies. It starts from birth. External influences begin with baby-mother interactions and expand through family and kin, carers, tribes, and social groups. Ultimately, this process generates culture, which is not genetically determined but is associated with superimposed social structures, with their attendant habits, mores, and cosmologies. From the earliest human cultures, shared group activities and rituals have evolved from food gathering, hunting, eating together through ritual performances of dance and music to great complexity. Even so, largely subconscious synchronisation of human behaviour can still occur, for example, walkers falling into step, the unison chants of spectators at a sporting event, or the whole audience swaying in time to the rhythm of music at a concert.
- HM Smith (1935): Synchronous flashing of fireflies. Science 82, 151-152. ↩︎
- J Sokol (2022): How Do Fireflies Flash in Sync? Studies Suggest a New Answer. Quanta Magazine. ↩︎
- S Camazine et al (2001): Self-Organization in Biological Systems. Princeton University Press. ↩︎
- A Cavagna et al (2010): Scale-free correlations in starling flocks. Proceedings of the National Academy of Sciences USA 107, 11865-11870;
A Procaccini et al (2011): Propagating waves in starling, Sturnus vulgaris, flocks under predation. Animal Behavior 82, 759-765. ↩︎