Human subjects

Dealing with people is difficult, especially if they are subjects in a scientific experiment. They may differ wildly in terms of their prior VR experience, susceptibility to motion sickness, suspicion of technology, moodiness, and eagerness to make the scientist happy. They may agree to be subjects in the experiment out of curiosity, financial compensation, boredom, or academic degree requirements (psychology students are often forced to participate in experiments). A scientist might be able to guess how some people will fare in the experiment based on factors such as gender, age, or profession. The subject of applying the scientific method to formulate and evaluate hypotheses regarding groups of people (or animals) is called behavioral science [154].

One of the greatest challenges is whether they are being observed ``in the wild'' (without even knowing they are part of an experiment) or if the experiment presents stimuli or situations they would never encounter in the real world. The contrived setting sometimes causes scientists to object to the ecological validity of the experiment. Fortunately, VR is a particular contrived setting that we want to evaluate. Thus, conclusions made about VR usage are more likely to be ecologically valid, especially if experimental data can be obtained without users even being aware of the experiment. Head tracking data could be collected on a server while millions of people try a VR experience.