emergence refers to the way complex behaviours and patterns arise out of a simple set of rules or interactions. An emergent behavior or emergent property can appear when a number of simple entities (agents) operate in an environment, forming more complex behaviors as a collective.
The emergent property itself may be either very predictable or unpredictable and unprecedented, and represent a new level of the system's evolution. The complex behavior or properties are not a property of any single entity, nor can they easily be predicted or deduced from behavior in the lower-level entities: they are irreducible. The shape and behavior of a flock of birds for example is a good example. One reason why emergent behavior is hard to predict is that the number of interactions between components of a system increases with the number of components, thus potentially allowing for many new and subtle types of behavior to emerge.
The term "emergent" was coined by the pioneer psychologist G. H. Lewes, who wrote:
"Every resultant is either a sum or a difference of the co-operant forces; their sum, when their directions are the same -- their difference, when their directions are contrary. Further, every resultant is clearly traceable in its components, because these are homogeneous and commensurable. It is otherwise with emergents, when, instead of adding measurable motion to measurable motion, or things of one kind to other individuals of their kind, there is a co-operation of things of unlike kinds. The emergent is unlike its components insofar as these are incommensurable, and it cannot be reduced to their sum or their difference."
(Lewes 1875, p. 412)(Blitz 1992)
An emergent behavior or emergent property can appear when a number of simple entities (agents) operate in an environment, forming more complex behaviors as a collective. The emergent property itself may be either very predictable or unpredictable and unprecedented, and represent a new level of the system's evolution. The complex behavior or properties are not a property of any single entity, nor can they easily be predicted or deduced from behavior in the lower-level entities: they are irreducible. The shape and behavior of a flock of birds for example is a good example.
One reason why emergent behavior is hard to predict is that the number of interactions between components of a system increases with the number of components, thus potentially allowing for many new and subtle types of behavior to emerge.