At present, there are a wide array of relatively distinct technologies which are often referred to as 'virtual reality', and which can sometimes be a source of confusion for those unfamiliar with the area. Broadly speaking, different VR technologies can be distinguished according to the level of immersion they offer. VR pioneers such as Jaron Lanier have emphasized this point, highlighting the fact that frameworks which are often referred to as 'virtual reality' enable participants to do little more than "just looking around in a spherical video". Lanier, along with other HCI researchers, has made a point to distinguish those technologies which afford reaching out to touch the virtual world versus those that do not: If you can't reach out and touch the virtual world and do something to it, you are a second class citizen within it... a subordinate ghost that cannot even haunt. Mel Slater schematizes different VR technologies according to the level of immersion which they offer -i.e., any VR technology's level of immersion can be defined relative to another VR technology by determining whether its affordances enable it to simulate in principle (or not) the experiences enabled by an alternative VR technology. So a specific VR technology A is 'more immersive' than another VR technology B so long as A could be designed (in principle) to simulate the experience of using B.