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Technology Panel Abstracts

EP6A: Cross Platform Aspects of Simulation Science VR Simulators: Why High Fidelity is Not Always Better

Scerbo, Mark W.

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Simulation In Healthcare: The Journal of the Society for Simulation in Healthcare: December 2007 - Volume 2 - Issue 4 - p 285
doi: 10.1097/01.SIH.0000303462.41493.3d

There is a great deal of interest within the medical training community regarding the level of fidelity needed in a simulation system. Researchers and developers in other high-risk domains such as aviation, the military, and power plant operations domains have also wrestled with this issue. The evidence indicates that high fidelity simulators do not always lead to better performance, and in some instances, can interfere with performance.


One of the primary reasons why high fidelity VR systems can compromise performance lies with a fundamental understanding of how humans perceive and process sensory information and how that information is depicted in VR displays. The mind actively engages in several processes that distort the perception of sensory information rendering a more stable impression of the world (eg, the psychophysical truncation of stimulus magnitude, minimizing stimulus differences through constancy, and implicit assumptions regarding absent stimuli). Often, these processes are not reflected in virtual displays and therefore interfere with the extraction of information.2 For instance, distortions in the representation of 3-dimenional space affect judgments about depth and the size of objects. Differences in lighting cues can also affect judgments of object volume and depth. Further, discontinuities across time can severely inhibit the ability to detect stimulus changes.

Moreover, we perceive the world through many sensory systems that function in parallel. Simulators that present information to only a few sensory systems (eg, vision and audition) exclude information that would normally be present for the other senses, requiring learners to invest additional attentional effort to compensate for the discrepancies between the genuine and the simulated environment. In fact, even the most sophisticated high fidelity simulators available for aviation or driving cannot reproduce the full complement of informational properties present in the operational environment, both within and across all sensory systems.

Further, there is an important distinction between perceiving realism and reality. A simulation that seems real is known to approximate reality.3 In fact, it would be an error to perceive a simulation training exercise as a real event. Thus, even “realistic,” high fidelity displays are not perceived to be real.


Given the discrepancies between genuine stimuli and their representation in virtual displays, one might well ask how much fidelity is needed. The answer to that question lies with the training objectives and to some extent, cost.2 Simulators support overall training goals and the level of fidelity needed should be tied to those goals. From the design perspective, fidelity issues can be addressed within the system analysis and development process used to establish the training objectives. An understanding of the training objectives may suggest design alternatives that use the lowest level of fidelity needed to meet the goals. Instructors too, may be interested in cost effective systems with lower levels of fidelity, but that satisfy their training objectives. Given the current status of medical training simulators, however, it is unlikely that developers or instructors will readily find solutions to all their fidelity issues. Thus, there is a real need for basic research on fidelity and performance issues specifically tied to medical simulation systems.


1. Smallman HS, St. John M: Naïve realism: misplaced faith in realistic displays. Ergon Des 2005;13:6–13.
2. Scerbo MW, Dawson S: High fidelity: high performance? Simulat Healthcare. in press.
3. Stoffregen TA, Bardy BG, Smart LJ, Pagulayan R: On the nature and evaluation of fidelity in virtual environments. In: Hettinger, LJ Haas MW (eds) Virtual and adaptive environments: application, implications, and human performance issues. Mahwah, NJ: Erlbaum 2003;111–1128.
© 2007 Society for Simulation in Healthcare