Full context:   The taxonomy is based on a character theory. This character theory consists of four characters: Achievers, Explorers, Socializers, and Killers (often mapped onto the four suits of the standard playing card deck; Diamonds, Spades, Hearts, and Clubs, in that order). These are imagined according to a quadrant model where the X axis represents preference for interacting with other players vs. exploring the world and the Y axis represents preference for interaction vs. unilateral action.