Extroverted Sensing and Introverted Feeling
The introvert, who directs his or her thoughts and feelings inward, is often shy, contemplative, and reserved. The extrovert, who directs his or her attention toward other people and the outside world, is usually outgoing, responsive, and aggressive. This typology is now regarded as simplistic because almost no one can be described as wholly introvert or extrovert. By definition, an introvert is someone who directs one's interests, mind, or attention upon oneself. The reason an introvert directs one's interest and attention inward is because that is where he/she is comfortable. Which is not to say that an introvert cannot make it as a successful PM, the argument is that extra effort will need to be expended.