Richard Skarbez in a Ph.D. candidate at University of North Carolina at Chapel Hill who has been researching how to measure presence in VR. Mel Slater has proposed that there are two key components of having the sense of presence that he elaborated in a paper titled “Place Illusion and Plausibility Can Lead to Realistic Behaviour in Immersive Virtual Environments.”

Slater describes the two components of presence by saying:

“The first is ‘being there’, often called ‘presence’, the qualia of having a sensation of being in a real place. We call this Place Illusion (PI). Second, Plausibility Illusion (Psi) refers to the illusion that the scenario being depicted is actually occurring… when both PI and Psi occur, participants will respond realistically to the virtual reality.”

Richard had poster at IEEE VR where he wanted to try quantify the impact of each of these two components. Richard used the phrase “immersion” to describe the feeling of Place Illusion & being in another place, and “coherence” to describe the Plausibility Illusion.

In his research, Richard set out to research the impact of both immersion & coherence through a VR experience and then using the standard battery of presence surveys including ones by Slater, Usoh & Steed and Witmer & Singer, as well as a number of other physiological and behavioral metrics.

What he found is that the presence survey scores were the highest when both the sense of immersion and coherence were strong. If either of these were weak, or if both were weak, then the presence scores were low, and there was no real statistical difference between those results these three conditions. He is finding that both immersion and coherence need to be present in order for there to achieve a strong sense of presence.

Interesting #IEEEVR poster on presence Immersion influences Place Illusion Coherence influences Plausibility Illusion pic.twitter.com/FXHQIem4b3 — KentBye Voices of VR (@kentbye) March 23, 2015

He also suspects that coherence is a lot more fragile than immersion. Immersion can be handled through a lot of technical innovations like low-persistent screens, low-latency head tracking, and high frame rates. However, coherence is more like a mental model that almost needs to maintain 100% logic in it’s construction. As soon as there’s something that doesn’t quite feel right, fit in the scene, or if there’s some uncanny valley-like behaviors, then the sense of presence can be broken like a house of cards falling. Richard says that most breaks in presence are due to a break in coherence and that while you can recover from it, it does take time.

Achieving a consistent coherence has a lot of implications in terms of choosing the fidelity of your VR experience. Richard reiterates that the uncanny valley isn’t just a one-dimensional issue that applies to just avatars, it n-dimensional because it affects every aspect of the VR experience.

If you’re designing a VR experience and want to achieve a photorealistic look and feel, then you’re going to need to achieve just as high fidelity in the sound design, the social and behavioral interactions of people, and perhaps even haptics. You may be able to create an incredible sense of immersion, but to achieve true presence then you’ll have to make the entire experience coherent based upon the expectations that the user has based upon their previous interactions with that stimulus or environment. If it looks real, then it better feel and behave at the same level of that visual fidelity.

Richard cautions against going overboard on the visual fidelity while ignoring the overall coherence of the experience, and it may actually create a better VR experience to strive for 100% coherence in your environment rather than 100% immersion through the visuals alone.

Richard talks about this spectrum from low-fidelity to high-fidelity by looking at some of the old 8-bit and 16-bit video games. He says that a lot of those games still hold up because they were able to maintain that complete coherence and consistency of what we might expect for how these games would behave. He says that the history of video games started to tread into that awkward uncanny valley in the PS2 & PS3 game console era when 3D games were first coming around, but that they had a number of glitches or behaviors that would take you out of the experience.

There’s still a lot more research to be done in this area, but to me it really holds true that the combination of place illusion with immersion and plausibility illusion with coherence are the two key factors from some of my most immersive VR experiences.

Finally, Richard talks about what he sees as the potential for that virtual reality embodied telepresence may be something that may eventually replaces the telephone or video VoIP like Skype. He sees that once the technology gets to be good enough that we might even start to use it for serious meetings such as seeing a doctor or meeting with a lawyer within a VR environment. It’s got a ways to go to get there, but he sees it as a viable short-term goal for a really powerful and potent application of this immersive technology.

Theme music: “Fatality” by Tigoolio

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