Hi, I wanted to save this Discord response here, since this is one of those common questions that comes up. I wrote this very fast, and may edit/refine this answer with time, but I'm just gonna post it as-is for now.
why four functions then instead of eight?
The purely theoretical answer is as follows: The possession of one of each energetic (Je/Ji/Pe/Pi) is perfectly capable of addressing any necessary mental operations, and the combined effect of functions can cover any gaps, without having to patch the theoretical hole with another four functions. For example, an Fe-lead who feels they are using Fi, can be evaluated as actually using Fe+Ti together, creating an attitude compound of I+F (or IF), which is nonetheless distinct from Fi-proper, via a defined criteria. Likewise for all the others. Additionally, 8-function models are theoretically problematic (i.e. falsification issues), and in many ways nullify the effort of typology altogether. Although 8-function viewpoints provide short-term explanations to certain overlapping psychic features, at least on the surface, believing in an 8-function model would nullify the belief in type, since it would mean there is no such thing as a discrete, dichotomous types. Therefore, insofar as we are of the belief that types exist as a physical reality, we should proceed aiming to identify something mutually-exclusive in human beings.
The hypothetical answer is as follows: CT speculates that there is something called an 'object-management' apparatus we all have, that is in charge of giving us a conscious awareness of objects. This is speculated to be neurologically connected, although the exact way is unknown as of now. It doesn't have to be as crude as brain-region-specific effects, but could also be more like neural cliques which rally together various regions to perform macro-tasks. And insofar as we are tying together functions to biology, we must acknowledge the constraints which that brings. The most important constraint is the brain and its processing power. Evolution is a very conservative enterprise, and it does not make sense for us to carry around another whole set/lump of functions 5-8, and yet largely never use them. Brain power is among the most caloric activities of the body, and if we had two object-management systems in us, that would be twice the load, for not much more payoff. As mentioned above, if the (seeming) gaps left by the unavailable functions - such as an Fe users IF dimension - can be covered by the net activity of Fe+Ti, there is no need or evolutionary pressure to also independently develop an Fi function.
Furthermore, an 8 function model raises the question of what it would even mean biologically: are there two copies of whatever biological analog is connected to Je, Ji, Pe, and Pi? If, for example, Je was somewhat connected to the Fp1 region, would one have two Fp1 regions? Obviously not. But it's worth considering that duplicate functions would mean postulating duplicate analagously associated biological tissues, which is an uncompelling argument from an energetically-conservative evolutionary perspective. A much more sensible hypothesis would simply be to say that Fe and Te (for example), and whatever underlying biological tissue it's connected to, are evolutionary bifurcations of each other. There is plenty of precedent for postulating this in the way the animal kingdom works. We can imagine a "root" biological function of Je, which took two evolutionary paths, and now people exist who have their Je in one variant, or in another. But having both is impossible for the same reason we don't have two heads. They are the same biological structure, and we only need one structure in our body-- therefore we have one, but of a given flavor. This would explain a lot of the data we see, which leads to the third reason:
Moving away from theory and hypotheses, what do we actually see? Well, we seem to see a largely mutually exclusive visual phenomenon. It's not perfectly exclusive, but before we jump to saying that this means signal mixing = biological mixing, we have to consider the symptomatic nature of visual signals. Vultology is a few steps removed from the root biology of type, and is "symptomatic" in nature; pointing to something else, the same way secondary sex characteristics (like broad shoulders and deep voices in men) are removed from XX and XY chromosomes. Thus, the confusion of symptoms is not automatically indicative of a mixed root reality, anymore than a woman with a deep voice and broad shoulders is mixed in her chromosomes. All things considered, it is actually amazing that a level of signal-exclusivity exists at all, at the vultological level, given how easy it would be to witness the opposite. If we all had all 8 functions, we would not see any significant degree of signal exclusivity, but instead we mostly see visual clusters form. This suggests that there is something biological in us that is "pushing" for mutual exlusion in the manifested effects of people, despite the superficial overlaps that we see due to how many noise variables we are not yet accounting for in our methodology. In more controlled scientific experimentation, we may find the exclusivity is higher than what it appears when we type 'in the wild' without truly controlling for makeup, age-rage, anatomical differences, physical conditions, and so many other things that may be upping the signal-mixing in ways that would vanish when fairly tested.
Additionally, we see hereditary trends in types, such as whole families of Deltas or Betas, and this suggests axes may be passed down genetically. We still have to explore this further, but it does point to the possibility of genetically rooted, exclusive function axes. And so, from a statistical angle this also compels the theory to side with function-axes exclusivity as the best interpretation of the data seen so far.
The possession of one of each energetic (Je/Ji/Pe/Pi) is perfectly capable of addressing any necessary mental operations
and the combined effect of functions can cover any gaps, without having to patch the theoretical hole with another four functions.
Ji -> abiotic = Ti
Je -> biotic = Fe
Ti -> Fe = IF
Fe -> Ti = ET
Ji -> abiotic -> Je -> biotic = IF ---- instead of Ji -> biotic
Je -> biotioc -> Ji -> abiotic = ET ---- instead of Je -> abiotic
The question: why theory assumed that energetics in psyche/nervous system are rigidly bound to the biotic/abiotic "lenses" (or other biotic/abiotic cathegory)? It seems that if there is no such fixed relation then we wont see hole in theory and instead more elegant solution. Such fixation needs explanation I think.
And insofar as we are tying together functions to biology, we must acknowledge the constraints which that brings.
The most important constraint is the brain and its processing power. Evolution is a very conservative enterprise, and it does not make sense for us to carry around another whole set/lump of functions 5-8, and yet largely never use them.
Right! But there is another strategy that can help save mental energy power. Processing biotic and abiotic informations at the same time can consume too much energy instead of directing processing power to one plane.
Nardi in his article writed:
Two Processing Circuits: To start, there are 2 circuits in the brain to process incoming stimuli. One circuit is faster. It sends sensory data directly to the front of the brain, our executive centers, to quickly act on the data. This is a more extroverted style. A second circuit is slower. It sends sensory data to the back of the brain, to link with memory and information processing centers, to compare, contemplate, and collate the data before moving it on to the executives. This is a more introverted style.
Two Executive Centers: Now, we have 2 main executive centers: a “goal-focused” left pre-frontal cortex (J-related)* and an “open-ended” right pre-frontal cortex (P-related)*.
*) my addition
Now we can bring together Extraverting-Introverting and Left-Right pre-frontal bias to get 4 executive styles:
Expedite Decision-making: Proactively meet goals. (Je)*
Refine Decision-making: Clarify what’s universal, true or worthwhile. (Ji)*
Energize the Process: Seek out stimuli. (Pe)*
Monitor the Process: Reﬂect on data and perceptions. (Pi)*
*) my addition
there is a module that aids us in identifying stuff in our environment. (biotic/abiotic)* Some people invest more in identifying lots of people’s faces and emotional expressions, whereas other people invest more in identifying makes and models of cars, computers, or other objects. Of course, everyone does both.
*) my addition
I think we can conclude that we don't carry around another functions and even standard functions at all. Instead we have potential to manifest one of the 8 possibilities that we will see as a function. I think I need to write this with less jargon. What I mean Ti user have some potential and connections between refine decition making-style (Ji) and module aimed at biotic plane but his brain simply don't usually use that route becouse of his stable "habit". He can manage his adaptation to the enviroument (objective-object-oriented and social) in different ways. At some unconcious level connections for other route of processing can still be active in dormant state but don't play any operational role. Maybe in some situations this routes can be activated and can produce manifestations of other functions characteristics - I don't know.
the same way secondary sex characteristics (like broad shoulders and deep voices in men) are removed from XX and XY chromosomes. Thus, the confusion of symptoms is not automatically indicative of a mixed root reality, anymore than a woman with a deep voice and broad shoulders is mixed in her chromosomes.
I am not biology expert but I heard about species where sex change is possible. If we continue this analogy I don't see a reason why we can exclude type changing. Although I also thing about it as unlikely.
If we all had all 8 functions, we would not see any significant degree of signal exclusivity, but instead we mostly see visual clusters form.
It's not perfectly exclusive, but before we jump to saying that this means signal mixing = biological mixing, we have to consider the symptomatic nature of visual signals. Vultology is a few steps removed from the root biology of type, and is "symptomatic" in nature; pointing to something else
We see visual clusters and also signals mixing. I agree that vultology is a few steps removed from cognition but biological status of functions seems not settled yet, and I don't know what conclusions can we draw from signal mixing.
Disclamer: I does not sympathize with any of 8 functions model as I also think we will missing the point if we accept it. In terms what we can observe and what meaning we get from type theory. Although I don't want to exclude a possibility for operational ability to activate something what we could name as a function. Becouse I think in our brain we have every needed component for other axis. I would like to propose a change in perpective in how we think about the functions. From something we/our brains/our minds/our biology "have" to something our brain/mind do habitualy in stable manner by specific and usually exclusive patterns of brain regions activation.
No that's not how genetic expression works.
Nardi's work clearly demonstrate 4 different types of perception neural architecture. The absence of pair mixing suggests judgement functions likely work in the same way, ie the genetic element allele is Fi/Te or Ti/Fe.
We also know the neural development generally operates on a pluripotent embryonic brain that becomes specialised in a use it or lose it fashion. Specialisation is successful.
So the base assumption should be 8 function neural architecture is present in all and usage preferences determined by genetic inheritance determines what become the preferential cognitive type.
So now if you apply Mendelian inheritance (based on having two copies of each gene) you can easily generate the observed division of types, because anyone who is homozygous (2 copies of the same allele) will be strongly pushed to using only one half of the brain architecture. Only a person with heterozygous genetics is likely to have delayed specialization, and thus the possibility of maintaining a larger range of usage across functions. This is especially true of this two loci combined preference system, because the vast majority of people will be homozygous in either the perception or judgement functions, meaning they will have a tendency to specialise in at least one direction. (and this is before I/E and J/P genetic promotion is considered)
From my own observation of various gifted celebrities it does appear that increased levels of intelligence do correlate with increased vultological cognitive expression range. Check out how James woods or Mel Gibson thinks (both are likely profoundly gifted). You will notice rapid switching between states and I'm pretty sure you will see strong usage of more than 4 functions.
Personally as someone who does have active use of shadow functions then you run into the major problem of competing values (Fe Fi clash is particularly bad), especially with Judgement functions. Shadow function use also creates enormous cognitive strain/energy drain. Biologically its not advantageous as it creates excess uncertainty. Even with an ideal neutral genetic make up, and the intelligence to bring shadow functions to conscious use level, it may still take an environmental push outside your comfort zone to gain conscious use of shadow functions.
@Robert Mitchell intersting.
I would put everything above in jungian frame.
When we talk about type we are speaking about ego structure in the psyche - 4 main archetypes which will go through process of differentiation. That's why I prefere 4 function model.
The rest from 8 possible functions stay unconscious in the shadow in undifferentiated state. They are still in psyche but don't play role in personality shaping.
My speculation is that - there is neuronal difference in the brain similar to that between being right- or left- handed person. But hardware - neuronal connections for operation are still there but in undeveloped way.
Ji -> abiotic = Ti
Je -> biotic = Fe
Ti -> Fe = IF
Fe -> Ti = ET
Ji -> abiotic -> Je -> biotic = IF ---- instead of Ji -> biotic
Je -> biotioc -> Ji -> abiotic = ET ---- instead of Je -> abiotic
I like this simple approach (simple in the Occam sense), having neural/cognitive modules shared among all individuals but whose interactions and manifestations vary based on interconnections. It seems more plausible to me to treat typology as an emergent property of more fundamental neurological characteristics, rather than assuming it is directly instantiated/referenced in a specific set of genes.
Additionally, while flat-out dimorphism does sometimes exist, sexual dimorphism being an obvious example, I think we can safely say it incurs a complexity penalty in this circumstance (though if someone actually knows evo psych and can counterargue, please do so!). And genetic variations in the connections between a set of shared modules can still lead to hereditary patterns in typology, without incurring said penalty (since we already know from neurology that such variations exist and that most mental modules are shared across humans).
This approach (introversion, extroversion, and tertiary-processing implementing the particular type based on connections to these two) can also be generalized to the Perception functions.
Say we have 3 modules, let's call them Overlay, Archive, and Matching. Overlay essentially creates a model of the world based on internal and external input, while Archive has a database constructed from past experiences and ideas; these modules are connected, since Overlay constructs its model using data produced by Archive, and Archive collects data from Overlay to build itself. Matching is used as a component (or 'consultant', perhaps) by both of these to do what its name implies, but in different ways.
If Matching uses fuzzy matching on Archive, but is stricter with matches to Overlay, then Archive Matching will be a lot slower to group, may never fully finish being grouped, and will be grouped by structural/subjective similarities (for example, all the various emotional connections that can emerge between seemingly-unrelated concepts due to our brains indiscriminately applying the 'fire-together-wire-together' principle). On the other hand, Overlay Matching will primarily be a matter of finding direct matches between sensory experiences and themselves or the Archive, and since it requires strict matches the Matching process will be faster.
If Overlay is higher-priority than Archive in this arrangement, most matching will be done as strict matching centered on the Overlay, giving us quickly-developing models limited by the quality of the user's sensations and prior knowledge, which can be then stored in the Archive and grouped into domain-specific trends and (more slowly) general patterns. This fits IS, as the Archive's lower priority leads it to focus more in information formatted as the overlay originally did, creating groupings of sensory details and overall experiences such as those Si tends towards.
If Archive is higher-priority than Overlay in this arrangement, most matching will be done as fuzzy matching centered on the Archive, giving us slowly-developing broadly-applicable groupings and relations between often-disparate sensory experiences, which can then be matched to aspects of direct experience to create seemingly-spontaneous updates of the Overlay as relations are applied to its current state and groupings narrow down search spaces. This fits EN, as the breadth of data collected by the Overlay increases the amount of matches to the Archive, which each expand the model in the Overlay, possibly leading to a feedback loop of Archived concepts constantly being related to and thus expanding the current experience.
If Matching uses strict matching on Archive, but is fuzzier with matches to Overlay, then Archive Matching will be quicker, and will be grouped by explicit compatibility between one structure and some component of another one (developing highly-modular frameworks of mutually-interacting sub-frameworks). On the other hand, Overlay Matching will primarily be a matter of finding approximate correlations between sensory experiences and themselves or the Archive, and since it requires fuzzy matches the Matching process will be slower.
If Overlay is higher-priority than Archive in this arrangement, most matching will be done as fuzzy matching centered on the Overlay, giving us moderate-speed grouping of sensory experience into objects and then correlations between objects (which are themselves treated as mental objects for further correlation), which can then be stored in the Archive and matched with other remembered fragments and (if a match is found) reintroduced to active mental space to be further processed by the Overlay. This fits IN, as this exploration of mental objects would lead to increasingly general models reminiscent of those produced by Ni.
If Archive is higher-priority than Overlay in this arrangement, most matching will be done as strict matching centered on the Archive, giving us moderate-speed development of a framework of highly-detailed interconnections (usually temporal or causal) between past events and ideas, which can then be matched to patterns in the current environment to create very quick updates of the Overlay as complex mental objects are recalled/produced from these matches. This fits ES, as with a broad enough database the quick updates of the Overlay based on matches to previously-encountered observational and behavioral patterns would almost match the speed of Se.
The above framework seems to replicate the 2nd order behavior (individual functions and function-compounds) of Perception with only 3 relevant categories: a Pe module, a Pi module, and an external matching system (uncertain whether this would be a single module or a framework of simpler modules), which can prioritize either strict or loose correlations (S vs N) based on the individual connection it has with the Pe/Pi module.
Incidentally, given the above model it feels intuitively like whichever system is doing fuzzy matching (the N function) also mostly handles the interaction between itself and the S function? Connecting Se to an Ni framework seems to require fuzzy matches to the 'fuzzy ideas' Ni contains, and the same goes for Si and Ne.
I'm not sure if this is accurate, however, so feedback on this (and on the rest of the post) would be appreciated!
The Ji/Je connections also seem to fit (both @Peter's ideas and the J/P connections), but I haven't processed those in as much detail.
EDIT: To add (since I hadn't initially realized it was part of this thread's discussion), this framework means that sufficient mental flexibility could allow you to switch how your Matching function is oriented (and presumably the same goes for the biotic/abiotic distinction). While you're correct that on their own, something like Se/Si would only be useful for an extremely broad and detailed Si database (since otherwise you simply wouldn't find matches even between related concepts due to the strictness), and Ne/Ni would quickly deviate into irrelevance (as fuzzy matches are done on fuzzy matches, without anything dragging you back to reality), if you could switch both connections you could go from an Se/Ni framework to an Ne/Si framework.
Each of these two 'normal' frameworks would have some trouble utilizing the information produced by the other, but concurrent development of Ne/Ni and Se/Si could provide both general and domain-specific translations based on these 'weird' frameworks, allowing for the real-time (speed vs breadth) and general-focus (generality vs precision) benefits of each of the 'normal' ones to be utilized depending on the situation.