"INFJs are deeply concerned about their relations with individuals as well as the state of humanity at large. They are, in fact, sometimes mistaken for extroverts because they appear so outgoing and are so genuinely interested in people -- a product of the Feeling function they most readily show to the world. On the contrary, INFJs are true introverts, who can only be emotionally intimate and fulfilled with a chosen few from among their long-term friends, family, or obvious "soul mates." While instinctively courting the personal and organizational demands continually made upon them by others, at intervals INFJs will suddenly withdraw into themselves, sometimes shutting out even their intimates. This apparent paradox is a necessary escape valve for them, providing both time to rebuild their depleted resources and a filter to prevent the emotional overload to which they are so susceptible as inherent "givers." As a pattern of behavior, it is perhaps the most confusing aspect of the enigmatic INFJ character to outsiders, and hence the most often misunderstood -- particularly by those who have little experience with this rare type."
- http://www.typelogic.com/infj.html