Keirsey’s four temperaments were based on language and tool using preferences – characterized by an abstract or concrete approach to language and cooperative or utilitarian uses of tools. It’s difficult to try to link Keirsey’s and Meyers’ systems too neatly. Keirsey divided the temperaments as abstract cooperators (NF’s) concrete cooperators (SJ’s) abstract utilitarians (NT’s) and concrete utilitarians (SP’s). For whatever reason, this system seems to have a great deal of appeal, perhaps because of the universality of the idea of four temperaments. Meyers was more interested in how the eight components interplayed and would look at personality and collect data based on many different combinations – introverted and extraverted judgers and introverted and extraverted perceivers as one example – the way in which people orient to the external world. Keirsey also wrote that his system was based only on what could be observed, rather than what was in people's heads, which was how he differentiated Meyer's system from his own.