From Dan Schawbel: There are four basic Keirsey Temperaments — SJ, SP, NT, NF — created by psychologist David Keirsey, who built on the work of the Myers-Briggs Type Indicator (MBTI). S stands for sensing, and the S’s are usually “concrete” in their approach. They concern themselves with things they can see, hear, feel, taste, and smell. N is for intuitive, and they focus on things they can imagine or things that could be. J and P refer to judging and perceiving, while T and F refer to thinking and feeling.