Collective behaviour allows a group of individuals to behave as a single unit eg. flock, school, swarm. This has the advantages of common and wider awareness of food/predators as well as confusing predators (safety in numbers). This behaviour is achieved by each individual following simple rules, such as: stay aligned with neighbours, match neighbours’ velocity, maintain fixed distance from neighbours, etc. This behaviour produces the illusion of orchestration.
Collective action allows a group of individuals to coordinate their actions. An example is quorum sensing, which enables honeybees to choose a new hive location. This mechanism is also used by bacteria to coordinate the release of digestive enzymes and toxins, and formation of biofilm.
Swarm intelligence allows a group of individuals to make better decisions than any single individual could. It has three main components: independence, diversity, and positive feedback. An example is an ant colony. One of the tasks of the colony is to locate and fetch food with a minimum expenditure of time and energy. Since no single ant is intelligent enough, or well-informed enough to direct this effort, swarm intelligence is employed. A few ants go out and explore for food. Individual ants explore independent routes. This makes for a very diverse and widespread search. Although most of them will find low-value, inefficient routes, a few will find more efficient routes to food sources. These will be the first to return to the nest, thus inspiring others to follow their path. The current hypothesis is that subsequent trekkers lay down pheromone at key junctions, thus reinforcing the best path(s) via positive feedback. Very quickly, the entire effort of the colony is concentrated on the most efficient route(s). A good decision has been made.
How does such swarm intelligence evolve? In the particular case of ants, why would scouts evolve to lead such dangerous, solitary, often fruitless lives? Isn’t that the antithesis of Darwinism?
The answer is that evolution applies not to individual ants, but to the gene pool of the species. It is the ants’ DNA that is evolving. Natural selection screens for those mutations that are beneficial to the colony. The more independent are the scouts, the more diverse will be the search for food, the greater will be the likelihood of success of the colony and therefore reproduction. The colony’s gene pool will then propagate the trait of independence in scouts.
Human intelligence allows a single person to be sentient. It incorporates mechanisms such as inference, pattern-seeking, goal-seeking, perception, complex memory, imagination, and language. However, it has been speculated that the basis of this higher intelligence may be some form of collective intelligence amongst neurons.