  Virtual Reality (VR) is seeing increased adoption across many fields. The
field of experimental cognitive science is also testing utilization of the
technology combined with physiological measures such as electroencephalography
(EEG) and eye tracking. Quantitative measures of human behavior and cognition
process, however, are sensitive to minuscule time resolutions that are often
overlooked in the scope of consumer-level VR hardware and software stacks. In
this preliminary study, we implement VR testing environments in two prominent
3D Virtual Reality frameworks (Unity and Unreal Engine) to measure latency
values for stimulus onset execution code to Head-Mount Display (HMD) pixel
change, as well as the latency between human behavioral response input to its
registration in the engine environment under a typical cognitive experiment
hardware setup. We find that whereas the specifics of the latency may further
be influenced by different hardware and software setups, the variations in
consumer hardware is apparent regardless and report detailed statistics on
these latencies. Such consideration should be taken into account when designing
VR-based cognitive experiments that measure human behavior.
