Some of the roots of role-playing games (RPGs) are grounded in clinical and academic role assumption and role-playing exercises.
Gary GygaxYou are not entering this world in the usual manner, for you are setting forth to be a Dungeon Master. Certainly there are stout fighters, mighty magic-users, wily thieves, and courageous clerics who will make their mark in the magical lands of D&D adventure. You however, are above even the greatest of these, for as DM you are to become the Shaper of the Cosmos. It is you who will give form and content to the all the universe. You will breathe life into the stillness, giving meaning and purpose to all the actions which are to follow.
Gary GygaxRole-playing games are contests in which the players usually cooperate as a group to achieve a common goal rather than compete to eliminate one another from play.... Role games ... bring players together in a mutual effort.
Gary Gygax