D&D historian Jon Peterson has taken a look at the concept of 'immersion' as it related to tabletop roleplaying games, with references to the concept going back to The Wild Hunt (1977), D&D modules like In Search of the Unknown, games like Boot Hill, and Forgotten Realms creator Ed Greenwood speaking in Dragon Magazine.
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Immersion and Role Playing in the 1970s
The idea that role playing involved a property called "immersion" occurred to the early adopters of the 1970s fairly early. The earliest e...