Hello! This is something that has been puzzling/troubling me for a little while...
I understand that the main theoretical difference between INTJs and ISTJs is that INTJs prefer Ni and ISTJs prefer Si.
Now, Si is usually associated with memories and ISTJs describe their thought pattern as using prior experience and memories as a basis upon which they can make their Te decisions for actions.
Does this mean that INTJs generally
don't refer to prior experience when making decisions (seeing as it's not preferred)? When is prior experience and memory used or 'factored in' by INTJs?
Cheers for any responses. Non-INTJ observations of INTJ behaviour are also welcome.
To be honest, I don't agree with the definition of Si as being specifically to do with recalling memories. To my mind, that is symptom of what it does, not the fundament.
I think of Si as a preference for information which is seen as certain or reliable. A primary Si will grade information according to how reliable they think it is, and the higher they rate it, the more it will feature in their decision making.
Prior experiences are absolute, in a sense, because what happened, happened. How much an ISTJ learns from these exoeriences will depend upon the individuals intelligence, which isn't really covered by function theory.
A less talented ISTJ may just think "We tired that and it didn't work, so I'm not doing it again". A smarter one will think something like: "We've tried that once, under a particular set of circumstances, and it failed. One trial is not enough to be certain, but this method is now unfavourable. Changing circumstances may invalidate this observation."
Indeed, things that happened in the past are more likely to have known outcomes, and so will attract the attention of ISTJs. An SJ will look at events in the past, and try to use them to predict what will happen in the future, so that they can steer a safe course.
Ni's, on the other hand, tend to look forward into the future to spy out some possibility they see as desirable, they try to see how that possibility can be brought about. To do this, they will often look to the past, to see how things have worked out and use that knowledge to help bring about the sought after future.
It is worth noting that Si and Ni are shadows of each other. Having on in the primary position forces the other into the 8th place - that is a shadow function, but the most potent one. Si and Ni underline each other. In an INTJ, Ni picks the outcome it wants, then shadow Si quietly supplies information to help Ni + Te reach a verdict. Ni is in the driving seat, but much of the sense of certainty that INJs experience comes from the shadow Si.
In an ISTJ, Si rules, but shadow Ni plays it part. It helps the SJ by pointing out possible futures that are worth avoiding. I also think it forms part of the judgement call as to which information is judged as reliable in the first place.