I think the concept of thresholds might be important in unraveling the mysteries of different psychological types.
A threshold is "the magnitude or intensity that must be exceeded for a certain reaction, phenomenon, result, or condition to occur or be manifested" (MacBook Dictionary).
Thresholds are already a working concept in neuropsychology, and some types of thresholds -- such as pain thresholds -- have already been well-researched. Some people react to pain at lower pain levels, while others are more resistant. The lower a threshold, the greater one's sensitivity.
Could it be that socionic types essentially differ on the basis of their thresholds for different kinds of stimuli? Or might threshold levels at least be a partial answer to the question, "what are the significant mechanistic differences between people?"
I see this "mechanistic approach" to personality as the opposite of socionics' more traditional "abstract logic" approach where logical categories are established and phenomena (people, interaction, information, behavior) are classified according to these categories, but 1) there is never absolute certainty as to whether the established categories are actually the most useful ones, and 2) the actual mechanisms by which the categories exist and operate are unknown.
The pitfalls of socionics' dominant methodology are well-known and far-reaching, and I feel like I talk about them in every other blogpost. The shortcomings of the mechanistic approach are 1) the slow pace of scientific progress and 2) the possibility that the results obtained through research will be too disorderly to be of much use to laymen. In my opinion, many socionists have a gut fear of disorderly scientific findings messing up their clear mental picture of things socionic.
But I digress. The mechanistic approach must be developed in socionics to bring it back to life and make it something more than a scientific conjecture (that is treated as fact by many of its proponents).
When looking for thresholds that may be significant determinants of interpersonal behavior and compatibility, I see no reason to assume that there must be 4, 8, or 16 such thresholds, or that the level of the threshold can be only "high" or "low," making it convenient to divide people into two discrete groups. Or that each threshold must be independent of the others (such as the four Jungian dichotomies), making it convenient to create a typology.
I would prefer to work from the bottom up, observing individual people and looking for thresholds, and basically any traits in general, that seem to play a significant role in their interaction with the world around them.
It is easiest to start with myself and people with a temperament similar to my own. From what I can tell:
- well-developed planning faculties, but unwillingness to make long-term plans (commitments) due to impulsivity (see below) and changeability of one's state
- low short-term self-control (things like leaving the house on time, abstaining from eating free cookies, or redoing one's work), but fairly high ability to make rational longer-term choices
- impulsivity as a result of low short-term self-control and changeability of moods and desires (a low threshold to a certain kind of stimuli?)
- waves of productivity as a result of impulsitivity; someone like this typically has to find a way to exploit one's changeable mental states in order to be productive, for instance by choosing an unstructured lifestyle and developing productive activities for each recurring state, and then engaging in each of them as the states change
- generally high threshold to signals from one's own body and to sensory signals in general; can easily take a mental interest in these areas via study or mentorship
- strong tendency towards mental absorption, which is a positive emotional experience; this absorption is often stronger than the demands of one's physical needs and almost always stronger than one's self-control, leading one to "overdo" things and neglect one's personal needs and external duties, if any
- great interest in information exchange with other people; a need to know what's going on in the spheres one is interested in and exchange information about it with other people
- low novelty threshold, and novelty is associated with positive emotional experiences; mental activity is easily stimulated by anything unexpected, unusual, and unfamiliar (however, this applies only to things that can provide mental stimulation: news, information, facts, activities, people, capabilities of other people, characteristics of the environment)
- as a result, one tends to use novelty as an "upper" to stimulate positive states and motivate oneself to act; lack of novelty is associated with boredom, lethargy, and indifference
- avoidance of pain and potentially painful situations (low pain threshold?), whether physical or interpersonal; this can lead to avoidant behavior patterns and an unwillingness to deal with problems
Clearly, this temperament "signature" is not unique to myself. Furthermore, it is clear that it has an evolutionary basis and serves a valuable societal function.
The observations above might be summarized as follows:
Societal purpose
This type is oriented towards the satisfaction of a certain kind of mental needs -- one's own and of society (hence the drive to exchange information). It specializes in the detection, processing, and conveyance of new and potentially useful information (news, trends, useful skills, tricks) and accumulates and exchanges this knowledge and skills with others, largely passing by information that is not easily conveyable. Where there is too much information available for one person to keep track of and process (such as in a complex society), a person of this type tends to develop niche interests and disregard other areas, in order to conserve energy.
Thresholds
Other, competing classes of needs -- physical and, to a lesser degree, social -- take a second seat to mental needs. This is probably accomplished through thresholds: mental states having to do with the presence or absence of new, interesting information (boredom/absorption, mental excitement level, a sense of prospects or the lack thereof) have low thresholds, meaning that they affect behavior powerfully, while physical needs have high thresholds (with the probable exception of one's pain threshold) and social thresholds are at medium levels.
Lifestyle
This type is poor at making commitments, exercising continual conscious discipline, or submitting to structure and external demands due to impulsivity, changeability of moods, lack of self-control, and high susceptibility to mental absorption. At the same time, the type is good at engaging in a wide range of activities fitted to its different states of mind.
In addition…
Challenges
Find ways to become an information specialist and exchanger without overstimulating yourself mentally and weakening your body and social relations. Develop a lifestyle that capitalizes on your high mental absorption potential and lack of self-control while steering you away from addictions (see
earlier post).
Who complements you
Most likely, people with high novelty thresholds, low physical thresholds, and medium social thresholds, who are also moody, changeable, and impulsive.
Some ideas
I would need to do some research on physiological and neural thresholds to build upon or revise what I've written above. However, I do have some ideas that might be applicable to socionics.
One is that

types are fundamentally interested in information exchange, while what

types are interested in can less easily be called "information" in the traditional sense of the world. It's more an experience or process, or perhaps a way of seeing things.
Another observation regards different types' response to what I call "novel information." Most

types I can think of seem to have a much more reserved, somewhat negative (mistrustful) response to novelty. They are more resistant to the influence of new information and tend to accept it only after it has ceased to be novel (at least in their particular social circle). Again, we have to be careful about defining "novel information" (which I won't try to do here).
It is tempting to try to associate each socionic function with some kind of threshold, and I try to resist this impulse. Nonetheless, I wonder if one might have a low threshold not only with the 1st function, but also with the 4th. The difference might be that the motivation with the 1st function is to embrace, while the motivation of the 4th is to avoid. In other words, the 1st function is easily stimulated with the purpose of embracing, while the 4th function is easily stimulated with the purpose of avoiding.
It is also tempting to continue on in this classical socionic spirit and hypothesize a "new socionics model" (whoop-dee-do) where each function number is assigned an approximate threshold level (High, Medium, or Low) and a positive or negative sign:
1: L+
2: M+
3: M-
4: L-
5: H+
6: M+
7: M-
8: H-
You analytical types can now pick that apart in search of symmetry and asymmetry and make it more elegant, but I am still convinced that this type of model gets us nowhere. It just teases a certain brain module without providing any real answers. Progress will be made by working from the ground up, collecting data, and trying to understand how specific neural mechanisms work.
So, it is more useful, in my opinion, not to look for thresholds that correspond to socionic categories, but rather thresholds that correspond to directly observed phenomena.
I find myself moving away from the classical socionics ideas that information can be divided into 8 categories and that when two types interact one function somehow conveys information to the same function in the other person. I'm not sure these concepts have much practical potential anyways (can they ever be tested?).
When thinking in terms of thresholds we can see that some bit of information might be "novel" and hence stimulating to one person and yet "old news" and hence uninteresting to someone else of the same type. Thus, it could be treated with interest or disinterest for reasons having nothing to do with type. The novel information (or old news) might be conveyed by a person of any type (imagine hearing a phrase such as, "have you heard about ________?"). Thus, something novel might be gleaned from someone who had no idea that he possessed novel information or qualities.
Note also that I am suggesting a definition of

quite different from Augusta's definitions: "the inner content and structure of an object" and "the object's potential energy." In practice I find that

types (ILE and IEE) are more about gathering, trying out, and conveying new and novel information than about "studying underlying phenomena" and "grasping the inner substance" (traits of analytic minds, perhaps?).