In structural coupling, it is structures, not systems, that do the coupling.
Autopoiesis alone cannot account for structural change. So the question that arises is, how can an autopoietic system evolve? How can politics, the economy, education, art, or any autopoietic system, adapt to a changing environment? Social systems are said to be operationally closed, which means they are self-organizing and self-reproducing; however, they are simultaneously structurally open. This means that an operationally closed system has other systems in its environment, and anything in a system’s environment has the potential to “perturb” or destabilize that system. The system then responds to perturbations by trying to re-establish internal stability, which is a dynamic, rather than static, stability. If social systems were structurally closed, they would immediately “freeze” because there would no need to change. But a structurally open system processes irritations from its environment and evolves.
Autopoietic systems cannot survive if they collapse into each other. However, this does not mean that systems cannot be coordinated in various ways. This is where organizations come into play. Organizations are social systems that make decisions, and they require some kind of membership; they have rules and procedures, usually hierarchies of authority, and mechanisms to expel members who aren’t contributing to the organization’s purpose or following the rules.
In terms of politics, social systems theory classifies governments as organizations. A government is not the political system itself because the political system is global and there is no global government, and the global political system differentiates itself internally through organizations like national and local governments, or any organization possessing the authority to make collectively binding decisions. A government, by coupling politics to the legal system, makes its own decisions subject to law. The public also has to believe that the government’s policies are rooted in laws that apply to the government as well. This coordination of function systems is one kind of structural coupling.
Luhmann borrowed the structurally coupling concept from Humberto Maturana. As Luhmann writes,
Maturana introduced the concept of structural coupling. The distinction [between this concept and autopoiesis] allows us to say that autopoiesis must function in any case since there would otherwise be no system. At the same time, it also indicates that coupling between system and environment concerns only structures [and not operations] and, as the case may be, everything in the environment that is relevant to these structures. Thus, on earth gravity is coordinated with the musculature of a living being that has to move in order to survive.
Another example Luhmann gives regards the brain. The organic structures of a brain evolve and change in response to environmental irritations, but the brain only selectively couples with its environment. The brain is able to develop its own complexity by limiting its openness to irritations, or by specializing. There are brain structures, or systems, devoted to processing various types of environmental stimuli.
Structures allow the creation of increased system complexity, and the system can respond, if the need arises, to environmental complexity. The structure emerges before it is found to useful. Presumably, structures arise all the time but then disappear because there is no use for them.
The mass media has developed structures (also called programs) to handle different kinds of information. The sections a newspaper reveal some of these structures: world news, national news, local news, business news, entertainment news, sports, arts and life, opinion, etc. These are all ways of dealing with the complexity of the mass media’s environment, or irritations from its environment. Internal complexity is built up when a structure is able to focus exclusively on one kind of information. Thus, for example, sports news has become quite complex, with many divisions and subdivisions. In sum, by limiting its openness to just one kind of environmental irritation, a system builds up internal complexity.
The advantage of structures is that they permit flexibility. The mass media system as a whole maintains its information/noninformation distinction; that doesn’t change, but structures can be established and dissolved as needed.