Within both research and practice, immersion is a topic that has received a lot of attention. The military, in particular, has invested a lot of time and money into creating "immersive" training environments in the hopes of providing personnel with training experiences that prepare them for many different types of encounters. Despite this interest, significant questions remain unanswered regarding the training value of such environments. A review of the literature on training in virtual environments reveals an assumption that higher immersion obtained through increased simulation fidelity results in improved training effectiveness and transfer. However, researchers who have attempted to evaluate this assumption have yet to produce compelling evidence. Further, there is no clear consensus regarding what constitutes immersion. For example, some researchers describe immersion as a state or feeling (e.g., Witmer & Singer, 1998), while others conceptualize it as a physical attribute of the training environment (e.g., Slater, 2003). This lack of agreement over the definition of immersion magnifies questions about its influence in the learning process.

Before the impact of immersion on learning and performance can be properly assessed, a clear operational definition must be provided that distinguishes immersion from other related concepts. Among other things, a meaningful definition will facilitate the development of good measures. Such measures are essential to any large-scale research effort because they provide standardization across efforts, including research evaluating the impact of immersion on training effectiveness. Therefore, the purpose of this paper is to provide a multilevel operational definition of immersion, as well as methods for the creation and real-time measurement of immersion, as it relates to learning in training environments. This analysis is the first step in aiding training designers in determining what level of immersion is required to facilitate effective training.