The sixteen relations this site uses are not derived from a classification of personality. They are assembled as a system on the foundation of a different theory: how people process information. That is why compatibility can be produced as a structure.
The starting point is the concept of information metabolism proposed by the Polish psychiatrist Antoni Kępiński.
Just as the body takes in food, uses what it needs and passes out what it does not, the mind also takes in information from the outside world, processes it and puts it out. That is how Kępiński saw it. In the same sense as breathing or digestion, there is a metabolism of information.
This is the important part: it is not a theory for classifying personality. It is a theory for seeing a person as a system that processes information. Seen as a system, what happens when two systems are connected can be thought about from the structure.
From the 1970s into the 80s, the Lithuanian researcher Aušra Augustinavičiūtė turned this idea of information metabolism into a concrete model.
Divide the information handled into eight kinds of element, and sort out which position in the mind each is placed in. The position where you are strong, the position where you strain, the position you want to leave to others, the position that does not rise to consciousness. Arrange eight elements in eight positions and the combinations that hold come to exactly sixteen. These are the sixteen types.
There is vocabulary borrowed from Jung's typology. But the principle at work is information metabolism, a different lineage from theories whose purpose is to describe personality.
This is the most distinctive feature of the theory.
Each type is defined as an arrangement of eight elements. So when the two arrangements are laid over each other, where they fit and where they do not is decided automatically. Does one person's strong position land on the position the other wants to leave to someone? Are both weak in the same position? Does it flow in one direction only?
Count the patterns of overlap and these too come to exactly sixteen. The sixteen relations are not a list gathered from observation but a consequence that comes out of the model.
The mechanism differs from counting how many of four letters match. Counting matching letters does not produce the kind of fit. Only a score. With a model of arrangement, the kind comes out. That is why this site returns not a score but a shape.
Do the relations derived from the model apply to real human relationships? On this point, confirmation by observation has continued since the beginning.
In Augustinavičiūtė's own survey, when married couples were classified by combination of type, the combinations corresponding to duality were reported to make up 45%. If the sixteen relations appeared evenly, it would be around six percent.
Since then, surveys and case collections in the same framework have continued for over forty years.
The use leans toward organisations rather than individual diagnosis. Team formation, staffing, recruitment, personnel audits. Deployments by people connected with the International Institute of Socionics are said to extend to more than 120 companies in Russia, Ukraine and the Baltic states. It has also been used in workplaces where a limited number of people stay in one place for a long time, such as far-northern sites.
There is more than one school. The line of the International Institute of Socionics and the line of Viktor Gulenko's humanitarian socionics are the main ones, and they differ in the interpretation of functions and in diagnostic procedure. The same term can point to something slightly different depending on the school, so when reading sources the quickest way is to check where they come from.
On the other hand, this theory is little known outside the former Soviet sphere. Serious introduction to the English-speaking world began only in the mid-1990s, and material readable in Japanese is still limited.
The definitions and names of the sixteen relations are used as they are in this system. Changing the names independently would make them impossible to check against other sources.
On the other hand, the reading of the four-letter types and the way each relation is described have been reassembled independently for readability. How the four-letter types are handled is written separately.
Explanations of this theoretical system (socionics) in Japanese, a 32-type diagnostic, courses and source material are at the official site of the Japan Socionics Association. This site is built on the Association's theory, taking out only the part about the relation between two people.
What kinds of fit there are can be read from the list. If you know the two types, you can also see at once which one it is.
To the sixteen relations