A Real-Time Low-Latency Hardware Light-Field Renderer by Regan, Miller, Rubin & Kogelnik (1999)

"We have developed and implemented a graphics system architecture for displaying static light fields with very low latency. A user test of the system revealed an average detectable latency threshold of 15ms, although some users were able to detect 7.5 ms of latency"

Head Tracking Latency in Virtual Environments: Psychophysics and a Model by Adelstein, Lee, Ellis (2003)

"a design guideline for HMD-based VEs that emerges from this study’s JNDs suggests that, to be imperceptible, system latency must be no higher than 17 ms. For some conditions or individual observers, this latency may have to be smaller still"

Perceptual Sensitivity to Head Tracking Latency in Virtual Environments with Varying Degrees of Scene Complexity by Mania, Adelstein, Ellis, & Hill (2004)

"In general, the results for JND from the present study overlaps well with the 8 to 17 ms JNDs measured in earlier investigations with an immersing HMD [Adelstein et al. 2003] as well as with the 19 ms JND we estimate for [Regan et al. 1999]’s nonimmersing desktop CRT system. [...] The consistency of the present JNDs derived from synthetic environments of differing visual complexity suggests this range may be a fundamental attribute for human perception of latency. However, this supposition is based on observations from systems with a 60 Hz update rate. "

MTBS3D - The Sony HMD is real! John Carmack (April 05, 2012)

"I believe the threshold for truly immersive VR is under 20 milliseconds"

Latency – the sine qua non of AR and VR by Michael Abrash (December 29, 2012)

"I can tell you from personal experience that more than 20 ms is too much for VR and especially AR, but research indicates that 15 ms might be the threshold, or even 7 ms. [...] So we need to get latency down to 20 ms, or possibly much less."

Oculus VR Best Practices Guide

At Oculus we believe the threshold for compelling VR to be at or below 20ms of latency.

When latency exceeds 60ms, the disjunction between one’s head motions and the motions of the virtual world start to feel out of sync, causing discomfort and disorientation; large latencies are believed to be one of the primary causes of simulator sickness.

If latency is unavoidable, it will be more uncomfortable the more variable it is.

It is worth noting that some research with head-mounted displays suggests a fixed latency creates about the same degree of simulator sickness whether it’s as short as 48 ms or as long as 300 ms;21 however, variable and unpredictable latencies in cockpit and driving simulators create more discomfort the longer they become on average. This suggests that people can eventually get used to a consistent and predictable bit of lag, but fluctuating, unpredictable lags are increasingly discomforting the longer they become on average.