Originally Posted by
BrainTypes.com
Jung coined Introversion from the Latin, meaning turning inward. Neuroscience tells us that an Introvert's brain is physiologically and neurologically programmed to reflect more than act on matters. Therefore, regardless of whether ISTPs are more on the outgoing or reserved side, they are far more reflective than their closest cousins, the ESTPs. One way this is manifested is that ISTPs normally find it more difficult than ESTPs to shut their brains off when trying to sleep at night.