Sussmann and Vanhegan (2000) define VR as a system that has as its goal the complete replication of elements of the physical world with synthesized 3D material. Due to this exact replica, the users essentially find themselves within the data, and complete immersion is achieved. The feeling of presence, which describes the degree of how much a user feels like they are at another place, is accomplished through the stimulation of various senses; most importantly there should be stated sight, sound, and touch. Through the clever implementation of these virtual worlds and the stimulation of multiple senses, the users are tricked into believing that they are experiencing everything in real life. In an ideal Virtual Environment (VE), the users can interact with the VE and manipulate it as it pleases them, making everything depending on their behavior. The importance of the human senses and the concepts of immersion and presence will be explained in more detail later on.
Guttentag (2010, p.638) defines VR very similar to Sussmann and Vanhegan (2000), by stating that “VR is defined as the use of a computer-generated 3D environment – called a ‘virtual environment’ (VE) – that one can navigate and possibly interact with, resulting in real-time simulation of one or more of the user’s five senses.” Gutiérrez et al. (2008) offer up a more detailed explanation of what navigation and interaction mean. They are two main activities that are usually conducted by users in VEs. Navigation describes the ability for users to move without restrictions in the VE, interaction implies the ability to interact with objects one is presented within the VE.
While the former is commonly available across a range of devices due to for example head-tracking technologies and motion sensors, the latter used to be problematic in past years. However, nowadays many developers are implementing both activities into their virtual offers. To achieve the illusion of a VE, different methods are applied. While it most commonly works by displaying the visual content through a head-mounted display (HMD) and other types of input devices adding to the virtual experience (Kim, 2005; Gutiérrez et al., 2008; Guttentag, 2010), there are some theoretical concepts underlying the whole experience.
While research used to be unsure about how to call which concept exactly (Sherman & Craig, 2003), this issue seems to have been resolved by now with terms being defined more clearly. In 2003, Sherman and Craig still describe that there are four key elements that a VR experience consists of; namely, they are “a virtual world, immersion, sensory feedback (responding to user input), and interactivity“ (p.6). It can be argued that this has been simplified until today, with the terms of presence and immersion being more commonly used throughout the literature and including the four key elements in their respective definitions. They are explained in the next sections.
The Importance of the Human Senses
There are several aspects that need to be considered when creating a VE. One of these aspects is the inclusion of the five human senses. While the sense of sight is commonly agreed upon as the most important sense for VR, there are other senses that can be addressed by technology nowadays (Guttentag, 2010). One of them is specified as hearing, referring to the 3D soundscape that we are exposed to in VR, another one being touch, also referred to as haptics. Thanks to technology, it is possible to include haptic feedback into virtual simulations as well. This is mostly achieved through vibrating surfaces, mimicking a sense of pressure, or gyro-apparatuses that shift our center of gravity (Gutiérrez et al., 2008).
Cheong (1995) recognized that the technology of VR at the time was still at an infant stage. Looking towards the future, he spoke of technological shortcomings that would be eliminated in the coming decades, allowing us to create virtual worlds with more realism, to a point where it will be indistinguishable from the real world. Additionally, he expected the olfactory (smell) and taste senses to be incorporated into future VR applications. While the two senses smell and taste are very important in our day-to-day lives, technological replication has not yet advanced far enough for them to play a significant role in the creation of VR experiences (Gutiérrez et al., 2008; Guttentag, 2010).
The Five Human Senses
As Pawaskar and Goel (2014) described recently, humans are a lot more likely to remember an experience by its smell than in comparison to its sound, sight or touch. This is mostly due to the fact that our nose is the only organ with a direct connection to the brain (Giordimaina, 2008). Previous reports have shown that if businesses can manage to implement an element of smell into promotional means, the promotions longevity can be increased significantly. The brain can interconnect smells with experiences so that an experience memory is triggered every time we smell a certain odor again. This emotional trigger can make guests want to relive their previous positive experience. Russel (2008; as cited in Pawaskar & Goel, 2014) states that scents can also be used to differentiate a product from the competition. Additionally, he mentions that the use of smells is proven to boost sales. This implies the great potential for the application in VR promotion once the technology has progressed towards a feasible implementation of those senses.
Immersion
The concept of immersion in VR relates to the physical configuration of the VR setup. Several distinctions can be made in between different VR systems, which are classified as follows (Gutiérrez et al., 2008):
Fully immersive systems have undoubtedly sparked the current hype and usually require the user to put on an HMD, fully enclosing the central part of our heads, covering eyes and usually ears. This complete isolation from the real world was hoped to increase the feeling of immersion users experience when putting on an HMD. However, this caused some problems with many users who had fallen sick when testing an HMD. The term to describe this sickness is called cybersickness. There are several identified causes for this, one being the occurrence of latency, the delay between a user’s movement and the transition thereof into the virtual world. Another identified reason is the constant movement in the simulation, but the fact that most users are standing or sitting still in real life. Nevertheless, several technological solutions have been developed recently to tackle the mentioned problems, they will be introduced further along the paper in the next chapter (Gutiérrez et al., 2008).
Semi-immersive systems usually rely on large projections or screens that are surrounding the user, and offer options for multi-user usability, such as CAVE systems, previously explained in chapter 2 (Gutiérrez et al., 2008).
Non-immersive systems are usually desktop based. They are available for a lower price and are most commonly found with customers of the video gaming industry, who find themselves to be very engaged into some exciting video game titles on an emotional level. Another example of this type of system would be mobile VR without the use of an HMD, such as watching a 360-degree video on a smartphone in non-stereoscopic (2D) images (Beier, 2003; Gutiérrez et al., 2008).
Presence
The second important concept in VR is presence. Due to its nature of referring to the psychology of each user, it is classified as being subjective (Guttentag, 2010). Presence is achieved when our consciousness believes that we are actually operating somewhere else – in a VE. The brain is tricked into believing it as fact by using the human senses mentioned earlier as an advantage for the VE. Only when the mentioned three human senses (sight, hearing, haptic) are externally stimulated, our brain can process the VE as legit and enable us to react to it on a more emotional basis (Steuer, 1992; Cheong, 1995; Lee, 2004). Several psychological cues have been identified to affect presence, for example, the predictability, emotional content, the use of plots (storytelling) and usage of background objects (Slater & Wilbur, 1997; Witmer & Singer, 1998; Bystrom, Barfield & Hendrix, 1999; Kim, 2005; Petkova & Ehrsson, 2008).
Researchers are clear about the fact that deep presence in a simulation can influence our feelings; if it is well crafted by its creators we can feel anxiety, happiness or even sadness (Gutiérrez et al., 2008). However, the aforementioned problems with cybersickness caused by high latency were not the only ones experienced in early stages of VR development (Mazuryk & Gervautz, 1996). Another interesting observation is that users are not known to lose their sense of presence due to possibly inferior visual qualities, but rather due to high latencies. Fortunately, technologies have caught up in development and nowadays HMDs function with a latency of mere fractions of a second, rendering the delay almost unnoticeable (Guttentag, 2010).
Due to the fact that emotions can be induced in a person through presence, VR has found a common application in therapy as a tool to treat phobias. Gaming addiction mostly exists due to the great presence players experience in good games, even though most of their desktop setups are non-immersive. Users feel as if they are in the VE and may find it more exciting than their real-world situation (Gutiérrez et al., 2008, Munster et al., 2015).
There are two different types of presence to be distinguished according to Kim (2005), one being non-spatial and the other being spatial presence. The former refers to the psychological aspect while the latter describes the physiological aspects. Spatial presence has since been replaced with the term immersion in more recent years. Kim (2005) claims that if a system is designed to generate non-spatial presence, a VR application is not needed. Only for spatial presence / immersion can VR provide a unique experience. While this can certainly be argued over, the author of this article does agree with Kim that VR technologies greatly influence the degree of immersion users can perceive.
Nevertheless, Sherman & Craig (2003) discuss how they were unable to identify a clear definition of presence and state that they only found contradictory information in literature at the time. In continuation, they define what they believe to be presence, namely the mental immersion, which matches with most definitions appearing in the more recent literature (Kim, 2005; Gutiérrez et al., 2008; Guttentag, 2010).