I've just taken a cognitive processes test that seems to indicate that I am an ISTJ. The "normal" tests always show that I am an INTJ. The problem I have is that I don't know how to answer a certain type of question like "You feel more comfortable sticking to conventional ways". I tend to stick to conventional ways, because if they are still used today, they must have some merit. If I decide it doesn't work as well as it should, I usually find a new and better way with little difficulty. I enjoy solving problems and "fixing" things, but only if I feel it's worth the effort. So does this mean I'm more S or N?
I would say no. To not think of something new because the old ways are proven and efficient is no indication for a N or S or whatsoever. That is more a logical decision.
To grasp the difference between N and S is difficult, because they are both perceiving functions, and furthermore the N function is something from the unconsious parts of the brain.
The main difference between N and S is that the first concentrates on meanings or relations between objects and the latter concentrates on the objects.
That could mean, for example an Extroverted Intuitor that is introduced to some new people at a party, will after the introduction not remember all of the names or how the people looked. But he will probably have a sympathy or antipathy feeling he can associate with the people, he just got to know. Or to describe it better, when it is not a feeling, it will be something like a mnemonic thing, like "The guy with grey hair works for a company, I can make sells to". Or "The boobs of the woman with brown eyes, where under no circumstances for real".
A Sensor draws these connections aswell but his important points lay elsewhere. For example: "The woman with the long brown hair, brown eyes and beautiful dress, whose name was Elise, made a very firm and gentle receiving when I was introduced to her. - She maybe works in a public relations job".
So the N is more likely to draw associations, while the S focuses on the tangible. This sort of behaviour but is only clearly visible, if you encounter MBTI types, who use it as a primary extroverted function.
With your type it is more difficult. You have either primary Si and Ne or primary Ni and Se. This is a complex combination and it cant be really picked out of the blind.
First of all I can recommend to you, as I always recommend, reading this post. This is one of the best functional analysis I have seen this far:
http://www.typologycentral.com/forums/nf-idyllic/4629-infj-profile.html
Secondly I can describe it in my words, but I am not very good at it.
The Ni has the same meanings and relationships thing going on like for example the primary Ne. But he does it not with all things, but just with those things he likes. So he is more selectively and has most of the times areas, where he is an expert and where he comes up with applicable new ideas or relations between things.
The Si on the other hand is more routinized. He has through his tertiary Ne the faculty to find new associations between the to him unknown things in the world, but he is not on the search for it like everytime. The Si is more inclined to have a community he lives, loves and works in that does not change and has its own rituals. I bet but that is just an assumption, when an Si is perfectly content with the situation he lives in, it is very unlikely that he will be ever going to change it. But then again, to be realistic, situations are less likely to be perfect.
My best friend is an ISTJ and there are two great faculties he is a master in. The first is strategy (ranging from war games to business) and soccer. You really can not beat him at any of those two and I know him for like 10 years now. He plays in both of his fields of intrest by the rules and he is constantly absorbing new information about for example new players in soccer teams or new business strategies on the market.
I had another good friend, who I would type to be INTJ. I knew him for like 8 years, but I knew him a bit earlier than the ISTJ. Our friendship eventually broke up, because I had had several changes of my lifestyle and he could not keep up with the pace my personality changed. So he quit the friendship, because he did not trust me anymore.
He in comparison to the ISTJ was very into sports too. He also knew every new player. He played an online game with the ISTJ, where you had your own soccer team. He sometimes lost, he sometimes won the season. I remember him saying about the ISTJ that he is too predictable to him. What was a mistake, because my ISTJ colleague then changed strategies to unconventional and bet him

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Furthermore the INTJ started to widen his intrest in sports. He started to explore new connections and possibilities and so he pretty soon became an expert on everything. You pretty could talk to him about american football, he knows a lot of the teams. I bet he even is intrested in gymnastics right now.
And that was not all. His intrest in sports and strategy within it, developed further until he found his profession, he had grown unbelievably professional at. Chess. I once played a game against him and I got so bored after the first two rounds, because he was waiting between moves for like 5 hours *lol*. I quit the game after the second round, because I had drunk my beer that fast that I could forfeit

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Another intresting fact is that he has become intrested in books aswell. Well he always was a big reader and in university he choosed the topic literature.
So what I wanted to say: If I were to ask my ISTJ colleague about developing intrest in some other sports besides soccer, he will surely make a joke of the sports game and then go back to soccer. He will, when he grows older, surely widen his intrest, but he will do it slowly. He has Ne and I have primary Ne, so we often exhibit a special cosmic quality in our meetings. When my ideas are reasonable and realistic, there is the possibility that he is drawn to them aswell and sees an epic possibility as I do. But this is most of the times only related to business strategies and to make cash. I can imagine that he and I will run some day our own business or at least work together.
The INTJ on the other hand is more likely to bring new aspects into his intrests, as long as they fit into his general intrest. He develops faster than the ISTJ towards his intrests. But he is the one that has grown a little bit out of reality and sometimes seems frightening. He has become a bit odd because he is fixated on his intrests and they start to interfere with a normal persons perception of reality. I do not know how he is today, havent seen him for like 3 years. Maybe I will give him a call...