# Models and Theories in Human-Computer Interaction/Wiener's Cybernetics

Cybernetics is a concept for explaining how complex systems (specifically with respect to animals and machines) organize their control and communication in order to achieve stability. It deals with inputs (or disturbances) from the environment and outputs (effects from a disturbance or stimulus in the environment) of the system, as well as a controller (e.g. the thermostat in a heating unit) which utilizes feedback loops (both negative and positive) in order to regulate the impact of the disturbance (or stimulus).
Cybernetics can be applied to many fields of study to explain complex systems: biology, sociology, anthropology, and information technology (to name just a few). It can be used to help predict the outcomes of various scenarios or explain the behavior of existing phenomenon. One that comes to mind is the body's immune system in the face of a deadly disease in which it attempts to eradicate. The human body consists of "controllers" called white cells which attempt to identify and eradicate foreign substances (disturbances) from the environment. It does this as a protective measure and in order to achieve homeostasis, a stable state (or corrective states) where foreign bodies are successfully dealt with.
Sometimes the foreign body is one that the system does not know how to cope with. For example, a disease like Ebola or AIDS. These are disturbances in which the controllers have no prior knowledge of and hence don't know how to contend with. The “knowledge" (or in cybernetic terms is called "transformation") within a complex system is essentially a set of rules defined by the input and the controller’s “reaction” to the input. The framework for dealing with these rules can be either deterministic or probabilistic. The former is essentially a predictable list of possible outcomes depending on the combination of inputs and set of actions that can be taken on the disturbance, while probabilistic is random in nature and hence is handled by a set of assigned probabilities in order to determine which actions to take. In the case of a disease in which the body does not recognize how to deal with, the probabilistic mode of options is implemented which can ultimately wreak havoc, as the immune system attempts to deal with this disturbance vis a vis an "unknown rule” the best way it can.
Another very important aspect of cybernetics is the interconnectedness of the system. The system is seen as a whole entity with distinct boundaries, consisting of interacting parts. What this suggests is a level of interdependence within the system.
The system, when dealing with its environment has a set of options it can choose from. How does the system know what to focus on and what to ignore? Constraints within the system provide focus and help to reduce the number of possible outcomes. The interdependence of variables also makes things easier since it does not need to worry about every single disturbance; so when one factor is affected in the system, there is a good chance that others are affected as well even though they may not be immediately apparent. This simplifies everything because one is dealing with less information. It also makes the system more predictable. A good example of interdependence making a system more efficient at identifying disturbances (once again within the field of medicine) is the recognition of symptoms one gets when undergoing a differential diagnosis. The differential diagnosis would be a clear path to understanding that there is a specific disease even though there might be other variables (symptoms) at work. All you really need to know is the symptom to be confident that the disease is what you think it is.