Iíve seen many forums discussing cognitive functions, but to my observations, the vast majority of such discussions were fortune cookie at best. Sometimes watching people discussing cognitive functions is as amusing and frustrating as watching a group of mentally retarded kids working with puzzle pieces. Where one cognitive function is fully explain in practice, and processed through as a stand alone, especially when this is done with Si and Ni. I've also seen pretty wild or invalid descriptions when dealing of such when it is relating with personality theory to how it is practiced.
Starting with the perceiving cognitive functions, there are function pairs Se/Ni and Ne/Si. Si and Ni are very dependant on Se and Ne respectively. To give an example of their differences and how they function, I'll use the ISTJ and the INTJ to keep all else constant.
So say that an INTJ observed that A causes B several times in his/her life. An Ni user will remember an A then B causal relationship very well. Then continues on with life where Se detects A in environment. Then the mind immediately recalls the pattern and the INTJ think "Wait I remember this, B is going to happen now". This is how the predictive ability of Ni works. It is basically anticipating. It's like flipping the patterns you have perceived in past situtions into the future and expecting them to repeat.
As composed to Si/NE with an ISTJ, a Si user collects data and streams them to find equilibrium (basic patterns). When a piece is collected which conflicts with the established pattern Ne kicks in and brainstorms ďwhy did this happen? What holistic change is needed in my equilibrium to be able to include this?Ē Itís like testing information against a query and updating the structure of the query for future use. The humorous title Inspector given to ISTJs is in referenced to this combination where unique pieces are what catch the eye of the ISTJ.
In short it would be
Observations from Se > Prediction through Ni
Brainstorming from Ne > Query through Si
(non linear> linear), in that Se and Ne can jump around and operate in no specific order, while Ni and Si are very straightforward when they operate when they process information in the mind.
These also repeat like Se>Ni>SeÖetc as a continuous cycle. Introverted perceiving functions require their extraverted counter part to interact first prior to individuals to be able to turn around the info in their heads. At least one of these cognitive pairs are used by every type with specialization directed either towards one. As with Ne/Si, both ENFPís and ISTJís use the same function pair, but a greater emphasis on a different part of the pair.
The function pair Te/Fi (and Fe/Ti) are less complex and people donít seem to trip up on them too much or at least from what I have judged. Often youíll see the grand simplification of Tís see objects and Fís see relationships. It services is purpose at any rate. It is based on what you place on individual value.
Te drops individual value to zero directed towards the environment, and thus in any XIXJ forums, you see a lot of criticism directed toward others. Fi holds value that elevates individual sense of self-worth, this leads to believing held values are worth implementing.
Where as Ti/Fe, Ti drops individual's value to nothing brought inwards onto the individual itself, which leads to self criticism holding internal thoughts to strict competitive standards, while Fe works to be friendly and cooperative with others in the environment.
I believe this explanation is slightly better than the cookie cutter pieces Iíve been reading on the majority of these forums. And in regards to S/N, I think people forget that they are perceiving functions and do not dictate views or specific actions. Anyways, critiques are welcomed or even new interpretations on the functions, hoping for a greater discussion on the topic, if you need me to expand on a certain part I will do so... so what are your thoughts?