Originally Posted by Reaktor
Very nice question. Temperaments are not definitive. Your personality type does show a tendency of having one temperament over another if you analize yourself from a global pov. However, note that the subtype DOES change slightly your temperament and can make you appear one or another, since temperaments are associated with functions and functions are associated with subtypes.
The dominant subtype correlates with linear-assertive. Creative with flexible-maneuvering. Normalizing with balanced-stable. Harmonizing with Receptive-Adaptive.
If you are a LSI, the basic description of LSI by default will resemble to a Normalizing subtype, in which the accentuated functions are Comfort Sensisng (Si) and Logic (Ti). However, life demands the individual to adapt to the context which life randomly creates, that struggle-facing or addaption is what define the strongest subtype in you, since you're forced to use X or Y functions more than others, they may not be your "strongest" ones.
Note that even if you're, for example let's say, a SEI-Dominant and people see some linear-assertive behaviour, that is not part of your core. From an holistic point of view, you should be able to see an accentuation of receptive-adaptive temperament in that SEI-D.
What's really important is to introspect and observe which temperament is more notable in you in general.
An important note is also to observe how you behave externally (when surrounded by friends, classmates, in the street, in the bar, etc) and internally (with your family, in your house, in your room). Usually extraverts will behave in a slightly intraverted way when alone and Intraverts vice versa. If externally you behave like an LSI, then most likely you're an LSI, since his external functions are intraverted: Ti+Si+Fi+Ni, and the internal functions are: Se+Fe+Ne+Te.
But don't think that when being in a internal context, when performing a task which require decision-making you will use the internal functions. No, you will use your decision making fucntions. For example Ti+ (If you're LSI)
Hope this helps you.