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IMMERSION AND SENS OF PRESENCE:
The feeling of presence and immersion are two concepts that continue to promote much interest among virtual reality researchers. An individual’s propensity to feel “enveloped by” or “present” in a virtual environment seems to be necessary, particularly in psychology, in order to offer a high level of quality with respect to therapeutic services delivered.
 
DEFINITIONS:

Immersion

The feeling of immersion, whether physical or psychological in nature, allows the sense of belief that the user as left the real world and is now “present” in the virtual environment (Sadowski & Stanney, 2002).

There are major schools of thought concerning the significance of the concept of « immersion » in a virtual environment. Witmer & Singer (1998) define immersion a psychological state characterized by the perception of being or feeling « enveloped by », « included in » or « in interaction with » an environment offering a continuity of various stimulatory experiences. They suggest that the factors affecting immersion include : (1) the isolation in the physical environment (2) the perception of feeling included in the virtual environment; (3) the state of « natural» interactions and of control perception; (4) the perception of moving within the virtual environment. These researchers add that virtual environments promoting a greater feeling of immersion will likewise produce a greater feeling of presence.

From a different perspective, other researchers have suggested that immersion is more likely a product of technology that facilitates the production of multimodal sensory “input” to the user (Bystrom, Barfield, & Hendrix, 1999; To drape, Kaber, & Usher, 1998; Slater & Wilbur, 1997). For example, Slater and Wilbur (1997) define immersion as being the extent to which a computerized system is capable of offering to the user the illusion of reality at once being: (1) inclusive, (2) vast, (3) surrounding and (4) vivid. According to them, inclusion occurs when the sense of physical reality is completely cut. The aspect of vastness in illusory reality (in virtual reality) demonstrates an adaptation a stimulation of a series of sensory modalities. The inclusiveness aspect signifies the extent to which the virtual environment is panoramic rather than being limited to a narrow field of vision. The sharpness aspect of the virtual reality refers to the degree of resolution and of the fidelity of the stimuli for each modality and it is concerned with the richness of the information, its content, as well as the quality of the virtual system. Slater and Wilbur (1997) also suggest that immersion may be subject to an objective description and may be quantifiable in terms of what the system can offer to the user. Based on the descriptors, they characterize immersion as being primarily determined by the measure of the systems and the system’s capacity to reproduce the physical sensation of the real world within a virtual reality environment with which the person is interacting. Slater (1999) is critical of de Witmer and Singer’s approach, suggesting instead that their perspective confounds the objective and physical properties of the virtual environment with the subjective aspects of the experience of presence.

Independently of the definition of immersion used in the virtual environment context, presence seems to be moderated as much by external factors as by the internal factors of the individual. In order to maximize the elevated degree of presence, it is important to place equal emphasis on the individual’s experiential immersion as well as on the virtual environment. In other words, the person should be sufficiently immerged within the virtual environment to allow for the apparition of a psychological sense of presence. Nevertheless, if the user becomes distracted or remains in contact with the external world, the sensation of presence risks never emerging or risks failing to strongly develop (Sadowski & Stanney, 2002).

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Presence

The notion of presence is considered to be central to virtual reality. Presence is traditionally defined by the psychological perception of being “there”, within a virtual environment (in which the person is immersed). Researchers agree on this definition despite the fact that each has added his/her nuances to the definition (van der Straaten & Schuemie, 2000).

For example, Barfield and Hendrix (1995) distinguish virtual presence from presence in the physical world insofar as the person believes that he/she is in a different place from the one that he/she physically experienced during the course of the experiment stimulation generated by the computer. From their point of view, Sheridan (1992) and Zelter (1992) describe presence as the physical feeling of being in a place other than the physical location that the user finds him/herself in. Sheridan defines two types of presence, that is to say “virtual” presence and presence in “teleoperations” or (telerobotic). Sheridan’s idea has since developed and accordingly, presence is perceived as a feeling of being transported into a synthetic place or a place created by a computer through the use of various systems (Sheridan, 1996).

Witmer and Singer (1998) have also adhered to Sheridan’s conception of presence which holds that presence is perceived as the feeling of being transported into a synthetic environment. This concept is the subjective experience of being in a place or in an environment, even if the people find themselves physically in another environment. Singer and Witmer (1997) describe also presence as a perceptual flux that demands the direct attention of the individual. They suggest that presence be based on the interaction between sensory stimulations, environmental stimulations and the internal tendencies of the person. The individual\s psychological perception of presence within a virtual environment is perceived principally as a by-product of the properties of immersion, and as being implicated in the virtual environment. Thus, presence in a virtual environment depends on the degree of attention of the user as they displace themselves in the physical environment.

Kim and Biocca (1997) suggest that, fundamentally, presence is the product of two factors: (1) “the arrival” or the feeling of being “there” in the virtual environment, and (2) “ the departure” or the feeling of not being there “there” in the physical environment. According to these researchers, “the arrival” (or one’s involvement in a virtual environment) occurs when an individual concentrates their energy and their attention onto a stimulus and the events happening in the virtual environment, thus permitting the augmentation of the degree of involvement or of presence.

Lombart and Ditton (1997) have attempted to offer another explanation of the concept of presence. The authors define presence as the perceptual illusion of non-mediation. Lombart (2000) explains in a more profound manner presence as being in a psychological state or having a subjective perception in which, even if the experience is generated by technology, a part or a totality of the individual’s perception fails to recognize the role of technology at the time of the virtual experience.

Zahorik & Jenison (1998) have proposed an alternate vision to this concept by suggesting that presence is felt during a response to a virtual environment if the user’s actions are equivalent to the type of response offered in the real world, in which our perceptual systems have evolved.

O’Brian, Büscher, Rodden, &Trevor (1998) for their part, perceive the feeling of presence as being an extension of the real into the virtual world rather than a “cutting off” of the presence of the real world. They emphasize the importance of daily activities where events in the real world and the competencies of orientation, of movements, and of interaction of the user are to be transposed into the virtual world.

Schubert, Friedman, & Regenbrecht (1999b) propose an interpretation of presence in terms of “concretized presence” (“embodied presence”). They suggest that the state of presence is the result of mental representations of actions that are possible in the real world. Accordingly, presence develops by way of representations created by the user creates via their own corporal movements in concert with the actions that are possible in the virtual world. The authors perceive this mental representation in terms of the result of an active interpretation of the virtual environment. This representation is composed of two elements: (1) direct attention on the virtual environment and the repression of the physical environment and (2) the mental representation of the space outside of the virtual environment in which the body can be displaced.

Heeter (1992) proposes differentiating the different types of presence that can be experience in the virtual environment. Nevertheless, it is important to note that the degree of presence varies a great deal from one person to another. Thus, the concept remains a subject for further clarification and requires more study:

  1. Environmental presence: environmental presence represents the extent to which the virtual environment reacts as function of the person during virtual immersion and as a function of the persons own reactions versus his/her actions.
  2. Social presence: Social presence exists only if many people co-exist in the same virtual environment. The presence of other people offers additional evidence that the environment truly “exists” and fosters the experience of strong presence. These people can also be represented by avatars.
  3. Personal presence: personal presence corresponds to the feelings of being present in a virtual environment as well as to the reasons invoked by the individual to explain this phenomenon.

Despite the many discussions concerning the concept of presence, the very usefulness of this construct has at times been put into question (Stanney, Mourant, & Kennedy, 1998). A global theory encompassing the characteristics contributing to the feelings of presence and of immersion is required. Many research studies are thus warranted and would permit the evolution of this concept with respect to the fields for which it is pertinent.

MODULATORS OF PRESENCE:

As mentioned previously, there are several internal as well as external variables that influence different forms of presence (see Table 1). Thus, the variables related to the system as well as to the individual seem to influence the degree of presence experienced in a virtual environment (Stanney & al., 1998). Seven influential factors that seem to affect the degree of presence experienced are as follows:

1- Facility of the interaction: Individuals having difficulty, whether with the navigation through the virtual environment or with the interaction with the environment during the carrying out of a task, will have an increased tendency to perceive the environment as not being natural and may risk feeling a decreased sense of presence. Billinhurst and Weghorst (1995) attempted to manipulate this factor in their study and found a significant relationship between the ease of interaction for users and the augmentation of the feeling of presence.

2- User’s sense of control: Witmer and Singer (1994) suggested that a greater degree of user control versus his/her actions in the virtual environment influences the degree of presence. They explain that the immediacy of the response, of the correspondence between he actions initiated by the user as well as the natural aspect of the interaction stimulates this factor of control in the user. Sheridan (1992) suggested that the user’s control in terms of his/her relation with the movement encoders and with the environment (e.g. the ability to modify one’s point of view) and the user’s ability to modify the physical characteristics of the virtual environment are principles that determine the feeling of presence. Welch, Blackmon, Liu, Mellers & Stark (1996) found that factors related to the interaction (versus passive observation) have quite a positive influence on the degree of perceived presence.

3- Realism: Witmer and Singer (1998) suggested that presence should augment with the degree of realism of the images in the virtual environment. The realism of the image in this context is related to the connection, the continuity, the consistence and the signification related to the stimuli presented in the virtual environment. Welch & al. (1996) found a positive relationship, albeit limited, between the realism of the image and presence. Wilson, Nichols and Haldane (1997) determined that detailed and realistic replicas were positively related to the sense of presence. Snow and Williges (1998) concluded that the resolution in the visual apparel and the texture of the images in the virtual environment, represent significant parameters, and are at least as influential as other factors (e.g. fields of vision, tracking of movements of the head). Other perceptual modalities (sound, touch, odors) may also contribute to the feeling of presence, but research in these areas has progressed slowly to date.

4- The length of the exposure: The preliminary results of research conducted by Stanney (2000) indicate that presence is not enhanced by the prolonged exposure. This study indicated that the virtual environment itself seems to promote a high level of presence (or not) within the very first 15 minutes of exposure. It would seem reasonable, thus, to anticipate that a longer duration would enhance presence because a longer immersion enhances other factors exercising an effect on the level of presence. These factors include the familiarity with the task required in the virtual environment, the level of sensory adaptation and the discordance of sensory-motor stimulations presented in the virtual environment. If the prolonged virtual exposure results in an augmentation of cybersickness, presence can be negatively affected. Witmer and Singer (1998) reported combined results from four studies that demonstrated a negative correlation between presence and cybersickness. The authors suggested that cybersickness distracts or deviates the user’s attention in the virtual environment. The user then concentrates on the internal feeling of faintness which diminishes involvement and reduces the feeling of presence. Stanney & al. (1998) also observed that the degree of cybersickness and of presence felt are correlated with a third factor (e.g. vection) whereby the change in one factor initiates changes in another one, but only via a third intervening factor. Independent of the relation between them, with respect to the factors that influence the feeling of presence, cybersickness represents one of the most harmful factors. Despite the fact that presence is important in virtual reality, the duration of the exposure should minimize as much as possible the intensity of cybersickness.

5- Social factors: the presence of other individuals (human or avatars) contributes to the subjective feeling of presence. If other individuals in virtual environment recognize the presence of the user in the virtual environment, this offers more evidence to the user that he/she “exists” in the virtual environment. Social presence can result from verbal or gestural communication and from interactions involving the user and others and may act as a form of confirmation that others recognize their own existence in the environment.

6- Internal factors: Salter and Usoh (1993b) describe internal factors in terms of individual differences as well as in terms of the way an individual cognitively manages the information provided by the virtual experience.

Slater and Usoh (1993b) suggest that subjective experience is encoded in terms of three main representational systems: the visual systems, the auditory systems and the kinesthetic systems. The authors maintain that people have a natural tendency to favor one system over another according to the given context. The visual system includes external images as well as internal mental images whether memorized or constructed. The auditory system includes the principles related to sound, including the auditory system linked to internal dialogue (speaking to oneself). The kinesthetic system includes tactile sensations caused by the external forces acting on the body and the emotional responses and emotional responses with involving the sensations. In another study (Usoh, Catena, Arman & Slater, 2000), the researchers measured presence in a physical environment versus in a virtual one where the participants reported experiencing the same degree of presence in reality as in the virtual environment.

Slater and Usoh (1993b) study suggested that the “visuals” promote more presence than the “auditory” or “kinaesthetic” factors. In addition, having the perspective of the first person (“I”) promotes a greater degree of presence when compared with the perspective of the second or third person. They also suggest that to a great extent, users’ visual affirmations and users’ references when describing the virtual environment (e.g. “seeing” or “looking”) have resulted in a greater tendency to feel presence. In environments involving avatars, the sense of touch permits the reporting of higher levels of presence. It is nevertheless important to interpret these findings with caution, seeing as the results describe a study using a virtual environment that stimulated the visual system primarily, involving only a small number of sounds and incorporating no kinaesthetic stimulation. It is also important to take into consideration the characteristics of the individuals using the virtual environment. The typology of these characteristics remains a controversial area of inquiry warranting more research.

7- System factors: Slater and Usoh (1993b) describe the factors of the system as being factors that are external. External factors are related to how well the system reproduces the real world, how the information is presented to the user and how the user interacts with the virtual environment. The external factors are determined entirely by the equipment and the software in use that together create and animate the virtual environment. They also suggest that external factors can influence the level of presence according to the their of quality, the resolution of the information presented to the user’s sensory organs in a way to not remind him/her of the virtual nature of the experience. The environment should permit the user to interact with objects and with other actors and to react in function of these actions. The researchers also suggest that the representation of the participant should include a virtual body with a silhouette that is similar to his/her own and with the capability of responding to the movements of the participant.

In a study on the factors related to the virtual system, Hendrix and Barfield (1996a) found that the addition of stereoscopic function positively influences both the degree of spatial realism during the interaction and the level of presence felt.

These factors do not influence presence in an equivalent manner. It has been suggested that the more the sensory modalities that are stimulated the higher the degree of presence. Sadowski (1999) also found a positive correlation between olfactory stimulation and performance, particularly if the performance demanded that the user remember or recognize an object in the virtual environment.

Gibson (1979) has used the concept of affordance to describe individual differences among users. More specifically, he has defined affordance in terms of the possibilities or the opportunities that the environment offers or permits to humans and animals. His theory of affordance suggests that perception, not only serves and controls what the user should do and not do (behaviors), but also that it depends on them (van der Straaten & Shuemie, 2000). The system offers to the user an ensemble of stimuli and each individual interprets and reacts in his/her own way as a function of his/her personal characteristics. This conceptualization thus insists expressly on the role of different interpretations that are made by on an individual basis of the stimuli that are proposed.

Despite the many discussions concerning the concept of presence, the very usefulness of this construct is at times put into question (Stanney & al. 1998). Stanney & al. (1998) suggested that presence could be intimately related to certain attributes of the virtual environment such as interactivity and involvement, which seem to be vital components in the creation of a believable or “realistic” virtual environment. For certain studies, the challenge may be to determine how to ameliorate the efficacy and the quality of the virtual experience rather than to attempt to arrive upon the ultimate solution regarding the concept of presence. Nevertheless, the feeling of presence in virtual environments, particularly in the entertainment and gaming industry, will without a doubt continue to take into consideration the element of presence as a desirable attribute to attract video game consumers.

Tableau 1. Factors that influence the level of presence

Properties
Explanation
The Ease of Interaction
Offers similar interactions allowing the people to orient themselves, to traverse and to interact with the VE*.
Interactions poorly created risk dividing one’s attention onto the movement/mechanism of the equipment instead of onto the virtual experience.
The Ease of Interaction
Allows immediacy of the response, the correspondence of user initiated actions, and the natural aspect of the control mode.
The delays, discordance between user initiated actions versus their representation by the system and the unnatural aspect of control offered by the system compromising the engagement in the VE.
Image Realism
Allows for continuity, consistency, the connection with and sense of presence with respect to presented stimuli.
Weak or poorly “designs” within the field of vision risk interfering with engagement in the VE.
Duration of the Immersion
Offering enough immersion time allows the user to familiarize him/herself with the task to be carried out in the VE and to permit a better sensory adaptation.
Avoid prolonged unnecessary immersion that could cause cybersickness.
Social Factors
Offer the opportunity to interact and to communicate with other avatars verbally or gestually allows other avatars to recognize the presence of the user in the VE and allows the user to have more evidence that he “exists” in a VE.
f the presence of an individual in the VE is not recognized by other avatars, this could affect the user’s perception that he “exists” in the VE.
Internal Factors
Identifying the characteristics of individuals that could promote presence.
Individual differences may make the virtual system differentially effective.
System factors
Follow the movements of the head, offer a broad field of vision, sounds, use of stereoscopic apparel, multimodal interactions and ergonomic software and equipment that create and animate VR and thus the feeling of presence.
A poor system risks to degrade the user’s virtual experience. Note: this does not necessarily imply achieving a perfect level of realism but rather suggest that the VE itself should be developed to the highest extent possible.

* VE = virtual environment

REFERENCES:

Barfield, W., & Hendrix, C. (1995). The effect of update rate on the sense of presence within virtual environments. Virtual Reality : The Journal of Virtual Reality Society, 1(1), 3-16.

Billinhurst, M., & Weghorst, S. (1995). The use of sketch maps to measure cognitive maps virtual of environments. In Proceeding of Virtual Reality Annual International Symposium (VRAIS ’95), pp. 40-47.

Bystrom, K.-E., Barfield, W., & Hendrix, C. (1999). A conceptual model of sense of presence in virtual environments. Presence : Teleoperators and Virtual Environments, 5(1), 109-121.

Draper, J.V., Kaber, D.B., & Usher, J.M. (1998). Telepresence. Human Factors, 40(3), 354-375.

Gibson, J.J. (1979). The ecological approach to visual perception. Houghton Mifflin Co.

Heeter, C. (1992). Being there : The subjective experience of presence. Presence : Teleoperators and Virtual Environments, 1(2), 262-271.

Hendrix, C., & Barfield, W. (1996a). Presence within virtual environments as a function of visual display parameters. Presence : Teleoperators and Virtual Environments, 5(3), 274-289.

Kim, T., & Biocca, F. (1997). Telepresence via television : Two dimensions of telepresence may have different connections to memory and persuasion. Journal of Computer-Mediated Communication, 3(2).

Lombard, M. (2000). Resources for the study of presence : Presence explication. Retreived on September 3rd, 2000 from: http://nimbus.temple.edu/~mlombard/Presence/explicat.htm.

Lombard, M., & Ditton,T. (1997). At the heart of it all : The concept of presence. Journal of Computer-Mediated Communication, 3(2).

O’Brien, J., Büscher, M., Rodden, T., & Trevor, J. (1998). Red is behind you : The experience of presence in shared virtual environments. Presentation at the Workshop on Presence in Shared Virtual Environments.

Sadowski, W. (1999). Special report : Utilization of olfactory stimulation in virtual environments. VR News, 8(4), 18-21.

Sadowski, W., & Stanney, K.M. (2002). Presence in virtual environments. In K. M. Stanney (Eds.). Handbook of virtual environments : Design, implementation and applications (pp. 791-806). Mahwah : IEA.

Schubert, T.W., Friedman, F., & Regenbrecht, H.T. (1999b). Embodied presence in virtual environments. Visual Representations and Interpretations, pp. 268-278. Springer-Verlag, London.

Sheridan, T.B. (1992). Musings on telepresence and virtual presence. Presence : Teleoperators and Virtual Environments, 1(1), 120-125.

Sheridan, T.B. (1996). Further musings and on the psychophysics of presence. Presence : Teleoperators and Virtual Environments, 5(2), 241-246.

Singer, M., & Witmer, B. (1997). Presence : Where are we now? In M. Smith, G. Salvendy, R. Koubek (Eds.). Design of computing systems : Social and ergonomic considerations (pp. 885-888). Amsterdam : Elsevier Sience Publishers.

Slater, M. (1999). Measuring presence : A response to the Witmer and Singer Presence Questionnaire. Presence : Teleoperators and Virtual Environments, 8(5), 560-565.

Slater, M., & Usoh, M. (1993b). Representations systems, perceptual position, and presence in virtual environments. Presence : Teleoperators and Virtual Environments, 2(3), 221-233.

Slater, M., & Wilbur, S. (1997). A framework for immersive virtual environments (FIVE) : Speculations on the role of presence in virtual environments. Presence : Teleoperators and Virtual Environments, 6(6), 603-616.

Snow, M.P., & Williges, R.C. (1998). Empirical models based on free-modulus magnitude estimation of perceived presence in virtual environments. Human Factors, 40(3), 386-402.

Stanney, K.M, Salvendy, G., Deisigner, J., Dizio, P., Ellis, S., Ellison, E., & al. (1998). Aftereffects and sense of presence in virtual environments : Formulation of a research and development agenda. International Journal of Human-Computer Interaction, 10(2), 135-187.

Stanney, K.M. (2000). Unpublished research data. University of Central Florida.

Usoh, M. Catena, E., & Arman, S., Slater, M. (2000). Using presence questionnaires in reality. Presence : Teleoperators and Virtual Environments, 9(5), 497-503.

van der Straaten, P., & Schuemie, M.J. (2002). Interaction affecting the sense of presence in virtual reality. Retreived on August 21st, 2002 from : http://graphics.tudelft.nl/vrphobia/intpres.pdf.

Welch, R., Blackmon, T., Liu, A., Mellers, B., & Stark, L. (1996). The effects of pictural realism, delay of visual feedback, and observer interactivity on the subjective sense of presence. Presence : Teleoperators and Virtual Environments, 5(3), 263-273.

Wilson, J., Nichols, S., & Haldane, C. (1997). Presence and side effects : Complementary or contradictory? In M. Smith, G. Salvendy, & R. Koubek (Eds.). Design of computing systems : Social and ergonomic considerations (pp. 889-892). Amsterdam : Elsevier Science Publishers.

Witmer, B.G. & Singer. M.J. (1998). Measuring presence in virtual environments : A presence questionnaire. Presence : Teleoperators and Virtual Environments, 7(3), 225-240.

Zahoric, P., & Jenison, R.L. (1998). Presence and being-in-the-world. Presence : Teleoperators and Virtual Environments, 7(1), 78-89.

Zeltzer, D. (1992). Autonomy, interaction, and presence. Presence : Teleoperators and Virtual Environments, 1(1), 127-132.