Immersion Revisited: A Review of Existing Definitions of Immersion and Their Relation to Different Theories of Presence

ISSN: 1795-6889 www.humantechnology.jyu.fi Volume 12(2), November 2016, 108 134 108 IMMERSION REVISITED: A REVIEW OF EXISTING DEFINITIONS OF IMMERSION AND THEIR RELATION TO DIFFERENT THEORIES OF PRESENCE The term immersion continues to be applied inconsistently within and across different fields of research connected with the study of virtual reality and interactive media. Moreover, immersion is oftentimes used interchangeably with the terms presence and engagement. This article details a review of existing definitions of immersion originating within the study of video games, virtual environments, and literary works of fiction. Based on this review, a three-dimensional taxonomy of the various conceptualizations of immersion is proposed. That is, the existing definitions of immersion may be broadly divided into three categories, each representing a dimension of the taxonomy: immersion as a property of a system, a subjective response to narrative contents, or a subjective response to challenges within the virtual environment. Finally, four distinct theories of presence are introduced and, based on the established taxonomy, we discuss how the individual theories relate to existing definitions of immersion. Keywords:immersion, presence, virtual reality, virtual environments, video games. © 2016 Niels Christian Nilsson, Rolf Nordahl, and Stefania Serafin, and the Agora Center, University of Jyväskylä DOI: http://dx.doi.org/10.17011/ht/urn.201611174652 This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 International License. Niels Christian Nilsson Department of Architecture, Design and Media Technology Aalborg University Copenhagen Denmark Rolf Nordahl Department of Architecture, Design and Media Technology Aalborg University Copenhagen Denmark Stefania Serafin Department of Architecture, Design and Media Technology Aalborg University Copenhagen Denmark Immersion Revisited 109 INTRODUCTION It seems reasonable to assume that most people will find it relatively trivial to explain the meaning of the concept immersion in relation to an object being submerged into a body of fluid. However, the same unambiguity does not exist when the term is used experience of media, such as the experience of virtual reality (VR). Following Blascovich and Bailenson (2011), we use the term virtual reality in a broad sense to describe any form of mediated reality and reserve the term virtual environment (VE) for systems relying on high fidelity tracking and displays to facilitate natural perception and interaction within an artificial all- (McMahan, 2003, p. 63). The term has come to stand for a multitude of different types of experiences and it is oftentimes used more or less interchangeably with concepts such as presence,involvement, and engagement (e.g., Lombard & Ditton, 1997; McMahan, 2003; Ryan, 2003). The inconsistent usage of the term immersion in definitions proposed by researchers probably has been exacerbated by the fact that it has been applied within a variety of domains. These domains include, but are not limited to, VE research (Slater, 2003; Witmer & Singer, 1998), video game studies (Adams & Rollings, 2006; Brown & Cairns, 2004; McMahan, 2003), film studies (Rooney, Benson, & Hennessy, 2012; Visch, Tan, & Molenaar, 2010), music studies (Dura, 2006; Ihde, 2007), and research dealing with linear and interactive works of literary fiction (Ryan, 2003). Furthermore, according to Lombard and Ditton (1997), the concept of presence has gained interest within a range of academic disciplines, including communication, cognitive science, computer science, engineering, philosophy, psychology, and the arts. The VE research and video game studies domains are particularly relevant because the two fields seemingly are converging (Zyda, 2005). The problem of inconsistent usage of the term immersion is twofold: The term has become diluted due to inconsistent usage, and the interchanged use of this and other terms may potentially confound the study of concepts such as presence that has been, and continues to be, regarded as central in relation to the study and application of VEs (Zahorik & Jenison, 1998). Consequently, through our research documented in the current paper, we sought to explore two questions: What meanings are associated with the term immersion and how do these meanings map onto existing views of presence? This paper provides readers with a review of the range of various meanings associated with the term immersion and clarifies how these views of immersion relate to different theories of presence. The remainder of the paper is organized as follows. First, we present a review of four general views of immersion: immersion as a property of the system used to display the virtual world, immersion as a perceptual response to that system, immersion as a response to narrative contents, and immersion as a response to challenges within the virtual world. This section is concluded with the introduction of a three-dimensional taxonomy of the different conceptualizations of immersion. Subsequently, we introduce four different theories of presence and discuss how the three dimensions of the taxonomy relate to the individual notions of presence. Finally, we present implications of our research and summarize and conclude upon the discussion detailed throughout the paper. Nilsson, Nordahl, & Serafin 110 METHODOLOGICAL APPROACH In order to explore what meanings are associated with the term immersion and how these meanings related to existing views of presence, a narrative literature review (Cook, Mulrow, & Haynes, 1997) was performed. Thus, unlike critical reviews, the selection of sources did not involve a comprehensive search of all potentially relevant work based on reproducible criteria. Instead, the review of literature related to immersion was based on relatively wellknown articles from dissimilar fields of study. That is, most of the selected articles have been cited more than 100 times and originate from VE research, video game studies, and research on linear and interactive works of literary fiction. For each of the conceptualizations of immersion we identified its relation to form, content, and the response of the user. The four theories of presence similarly originated from fairly well-known articles. Moreover, these four theories were selected because they represent different views of how presence relates to form, content, discussed in the concluding section of the paper. CONCEPTUALIZATIONS OF IMMERSION In her frequently cited book, Hamlet on the Holodeck,Murray (1997) provided the following reason for its ambiguous usage: Immersion is a metaphorical term derived from the physical experience of being submerged in water. We seek the same feeling from a psychologically immersive experience that we do from a plunge in the ocean or swimming pool: the sensation of being surrounded by a completely other reality, as different as water is from air, that takes over all of our attention, our whole perceptual apparatus. (Murray, 1997, p. 98) The general consensus seems to be that immersion involves being or feeling surrounded by something (e.g., Ermi & Mäyrä, 2005; McMahan, 2003; Ryan 2003; Slater, 2003; Witmer & Singer, 1998). However, a number of alternate propositions address what it is that surrounds the individual. One of the most prominent differences between existing views of immersion is the distinction between immersion as technology and immersion as a subjective experience. To use , some believe immersion to be an expression of how deeply one is submerged into a body of fluid, while others believe it to be the subjective experience of being submerged. More specifically, it seems reasonable to distinguish between four general views of immersion: (a) immersion as a property of the system used to present the virtual world; (b) immersion as a perceptual response to that system; (c) immersion as a response to an unfolding narrative, the characters inhabiting the story world, or the depiction of the world itself; and (d) skills. Throughout the following subsections, we present a review of these definitions of immersion. The definitions have been organized based on whether they qualify as a property of the system, a perceptual response, a response to narratives, or a response to challenges. The definitions are summarized in Table 1. It should be stressed that several of the cited authors adhere to multidimensional views of immersion, such as the one we propose. Immersion Revisited 111 Table 1.Summary of the Presented Definitions of Immersion. Authors A property of the system A perceptual response A response to narratives A response to challenges Slater (2003) System immersion: A property of the technology mediating the experience. The higher the fidelity of displays and tracking, the greater the level of immersion. Witmer and Singer (1998) Immersion: A feeling of being enveloped by, included in, & interacting with the virtual environment. Arsenault (2005) Sensory immersion: A sensation of being enveloped by the multisensory representation of the virtual world delivered via high-fidelity displays. Fictional immersion: The sensation of being mentally absorbed by fictional stories, worlds or characters. Systemic immersion: The mental absorption experienced when facing challenges that match including the challenges involved when exposed to nonparticipatory media. McMahan (2003) Perceptual immersion: The sensation of being surrounded by the virtual environment that increases proportionally with the number of modalities provided with artificial stimuli. Psychological immersion (immersion on a diegetic level): The mental absorption experienced during exposure to the world Engagement (immersion on a nondiegetic level): The state of focused attention on the game brought about by the desire for gaining points and/or devising a winning or spectacular strategy. Adams and Rollings (2006) Narrative immersion: A state of intense and focused attention on the story world & the unfolding events and acceptance of these as real. Strategic and tactical immersion: A state of intense preoccupation with observation, calculation, & planning or with swift responses to obstacles. Ermi and Mäyrä (2005) Sensory immersion: The feeling of being surrounded by the multisensory representation of virtual worlds delivered through large screens and powerful sounds. Imaginative immersion: The sensation of being mentally absorbed by a its characters. Challenge-based immersion: The mental absorption experienced when facing challenges requiring mental or motor skills. Ryan (2003; 2008) Narrative immersion: A state of intense focus on a narrative; can be divided into 3 subcategories: immersion (elicited by a strong sense of place and the joy of exploration), temporal immersion (caused by a desire to know what will happen next), and emotional immersion (brought about by emotional attachment to characters). Ludic immersion: A state of intense absorption in the task currently being performed. Nilsson, Nordahl, & Serafin 112 Immersion as Technology or the Experience of Technological Envelopment In relation to the study of VEs, the term immersion has been used to describe both the technology proponent of the former view, provided the following account of his view of immersion: from an objective point of view. The more that a system delivers displays (in all sensory modalities) and tracking that preserves fidelity in relation to their equivalent real-world Presence, para. 1) Immersion is therefore regarded as an objectively measurable property of the system and not we will use the term system immersion (Slater, 1999) when referring to this conceptualization of immersion. Proponents of the second view of immersion include Witmer and Singer (1998), who argued perceiving oneself to be enveloped by, included in, and interacting with an environment that provides a con Following this view, the subjective experience of immersion is influenced by at least three factors: (a) the extent to which the user is isolated from the external physical environment, (b) the sense of self-inclusion within the mediated environment, and (c) egocentric motion perception and the ability to interact naturally with the environment. It is worth noting that Witmer and Singer (1998) distinguished between immersion and involvement. The former relates to the sensation of being enveloped by the environment and the latter refers to the act of assigning great focus and attention to perceived stimuli and occurring events. Similar conceptualizations have been used to describe immersion in relation to video games. McMahan (2003) distinguished between perceptual immersion and psychological immersion that correspond to attentional surrender caused by system immersion and captivating stories and spaces, respectively. Particularly, McM many of the senses as possible to the outside world and making it possible for the user to perceive cMahan, 2003, p. 77). In a similar vein, Ermi and Mäyrä (2005) introduced the concept sensory immersion, referring to the audiovisual presentation of games. The authors described sensory immersion as follows: Digital games have evolved into audiovisually impressive, three-dimensional and stereophonic worlds that surround their players in a very comprehensive manner. Large information coming from the real world, and the player becomes entirely focused on the game world and its stimuli. (Ermi & Mäyrä, 2005, p. 43) Based on the presented definitions of immersion, it would seem that proponents of both views hold that immersion may be closely connected to media form, that is, the properties of the technological system used to mediate the experience. However, the fundamental difference is that immersion following one view is regarded as a property of media form, while the other Immersion Revisited 113 view stipulates that immersion corresponds to the subjective experience of the media form. Table 2 summarizes the two opposing views of immersion outlined in the preceding paragraph. Immersion as a Response to Narratives When discussing immersion in relation to video games, McMahan (2003) distinguished between the sensations of being immersed on a diegetic level versus a nondiegetic level. The l world in which the events of the unfolding narrative occurs (Prince, 2003). When immersed in a game on a diegetic level (i.e., psychological immersion), the player is mentally preoccupied by the world gs (2006) conceptualized immersive narrative immersion completely involved and accepting the Rollings, 2006, p. 30). Notably, a number of alternate definitions exist that resemble this one, albeit under different names. These include imaginative immersion proposed by Ermi and Mäyrä (2005) and Arsenau fictional immersion. In short, Arsenault discarded the label imaginative in favor of fictional based on the argument that this form of immersion needs not be explicitly dependent upon the imagination of the individual. According to Adams and Rollings (2006), an exhilarating plot, interesting character, and dramatic situations are prerequisites for the experience of narrative immersion. Thus, the term immersion has been used beyond descriptions of experiences elicited by interactive VR. Ryan (2003) described how reading may give rise to narrative immersion. Even though Ryan used the act of reading as her point of departure, she did not reserve immersion for experiences of nonparticipatory media. That is, narrative immersion may arise from any narrative work, However, Ryan provided an even more detailed account of what causes individuals to become immersed by narratives. Narrative immersion may be described in terms of the three subcategories: temporal,spatial and emotional. Even though her description of the three has Table 2. Immersion as Technology and Immersion as a Reaction to Technological Envelopment in Terms of Form, Content, and User Response. Terms Form Content User response System immersion (e.g., Slater, 2003) A property of media form describing the degree to which a system is able to faithfully reproduce natural perception and action through multisensory displays and tracking. System immersion is separate from content because it is used to describe the technology used to present the content rather than the content it self. Although system immersion may influence the user response, the reverse is not true. Immersion (Witmer & Singer, 1998), perceptual immersion (McMahan, 2003) and sensory immersion (Ermi & Mäyrä, 2005). Form factors, such as isolation from the physical environment and interfaces allowing for natural interaction, are believed to influence the experience of immersion. Content is generally not viewed as a factor influencing the subjective sensation of immersion. Immersion is view as a sensation of being enveloped by, included in, and interacting with an environment Nilsson, Nordahl, & Serafin 114 its roots in reading experiences, it may be pertinent to other forms of VR. Arsenault (2005) proposed that the three forms of immersion potentially could be used as subcategories of fictional immersion. Just as Adams and Rollings (2006) suggested that exhilarating plots are constituent to the experience of narrative immersion, so did Ryan (2003). She called temporal learn what will happen process by which the progression of narrative time distills the field of potential, selecting one branch as the actual, confining the others (Ryan, 2003, p. 141). the depicted location or scenery (Ryan 2003). It involves having a sense of place as well as the pleasure experienced when one is exploring the virtual space (Ryan, 2008). When discussing spatial immersion in relation to textual narratives, Ryan stated that, in its most complete form, e moments of sheer delight, the reader develops an intimate relation to the setting as well as a sense of being present to the experience of immersion resulting the protagonists or antagonists of the narrative (Ryan 2003). Ryan argued that this form of even when their causes are not real. Following the outlined definitions of immersion, it would appear that narrative immersion and its subcategories (temporal, spatial, and emotional) are characterized by a degree of mental absorption or intense preoccupation with the story, the diegetic space, and the characters inhabiting this space. Thus, narrative immersion is largely the product of the mediated content. Furthermore, when discussing spatial immersion, Ryan (2003) suggested that the media form also may be influential. According to Ryan (2003), pictorial media are able to instantaneously transport the viewer into the diegetic space. Textual media, on the other hand, involve a more gradual transition into the story world. This implies that the experience of spatial immersion accompanying exposure to high-fidelity displays resembles perceptual immersion (McMahan, 2003) and sensory immersion (Ermi & Mäyrä, 2005). Thus, spatial immersion may be influenced by both form and contents (i.e., system immersion may contribute to the sensation of spatial immersion). Table 3 summarizes the definitions of immersion pertaining to the experience of immersion brought about by exposure to narratives. Immersion as a Response to Challenges In addition to viewing immersion as the outcome of exposure to narratives, Ryan (2008) also acknowledged that immersion may arise from the experience of VRs devoid of explicit narrative contents. She referred to this form of immersion as ludic immersion and described it as an intense focus on the performance of a given task, akin to the intensity exhibited by some professional classical musicians. McMahan described immersion on a nondiegetic level as the . Ermi and Mäyrä referred to this form of immersion as challenge-based immersion and described it as (Ermi & Mäyrä, 2005, p. 43). Notably, they argued that this feeling of immersion may be brought about by challenges to both sensorimotor and mental skills. Immersion Revisited 115 Table 3. Immersion as a Reaction to Narratives in Terms of Form, Content, and User Response. Terms Form Content User response Narrative immersion (Adams & Rollings, 2006; Ryan 2003), imaginative immersion (Ermi & Mäyrä, 2005) and fictional immersion (Arsenault, 2005) May be experienced across different types of media May result from exposure to the events, characters, and world of an unfolding narrative Characterized by a mental absorption with the mediated narrative Temporal immersion (Ryan, 2003) May be experienced across different types of media Results from expose to the unfolding events, i.e., the plot Characterized by an intense preoccupation with the narrative due to a strong desire to know what will happen next Spatial immersion (Ryan, 2003) May be experienced across different types of media, but pictorial media is particularly effective at eliciting this form of immersion Results from exposure to the depiction of the narrative space Characterized by an intense preoccupation with the narrative accompanied by a strong sense of place and the pleasure of exploring the environment Emotional immersion (Ryan , 2003) May be experienced across different types of media Results from the experience of the depicted characters Characterized by an intense preoccupation with the narrative due to a strong emotional investment in the fate of the protagonists or antagonists of the narrative However, the two authors are of the belief that the challenges more often than not will pertain to both conditions to some degree. Whereas the simultaneous occurrence of both types of challenges is possible, one may argue that one of two conditions has to be met in order for the challenges to be experienced as immersive. Either the simultaneous occurrence of the challenges has to be brief enough to avoid attentional overload, or the user needs to be so proficient at tackling one of the two skills that he or she has the attentional surplus necessary to face the second one. That is, either task switching must be possible, or one of the two competing tasks has to be automated (Saariluoma, 2005). With these arguments in mind, it seems reasonable to distinguish between Adams and Rollings (2006) made exactly this distinction when describing the two forms of immersion: strategic immersion and tactical immersion. The former refers to the experience of being intensely preoccupied with trying to win the game. In other words, when strategically immersed, the player is almost entirely preoccupied with the optimization of choices and therefore ignores elements such as the story and characters (Adams & Rollings, 2006, p. 30). calculation, and planning. Tactical immersion refers to the form of immersion experienced when playing hectic action games where continuous demands for reactions to occurring obstacles give rise to complete attentional surrender. Particularly, repeated confrontation with relatively small g on other elements of the game, such as the general strategy or story (Adams & Rollings, 2006, p. 30). Notably, these definitions of immersion greatly resemble the experience of flow (Csikszentmihalyi, 1990), which also describes the experience of playing video games (Chen, 2007). Flow arises when an individual performs an activity of interest in which the perceived challenges correspond to the perceived skills. The state of flow is characterized by intense and Nilsson, Nordahl, & Serafin 116 focused attention, the merging of action and awareness, the loss of self-consciousness, a sense of control, a distortion in temporal experience, and the experience of the activity as being intrinsically rewarding (Nakamura & Csikszentmihalyi, 2005). Considering that challengebased immersion is most intense when the balance between challenges and skills is maintained, both strategic and tactical immersion may be accompanied by a subjective response similar to the state of flow. Thus, the types of immersion outlined in this subsection may be characterized by intense focus and attention brought about by the need for physical reactions to occurring obstacles or cognitive demands. Moreover, this implies that these types of immersion are influenced to a large extent by the mediated content because the challenges themselves are shaped by the subject matter. Even though the cited authors do not explicitly address the role of media form, it does seem likely that it also influences challengefield of view the vertical and horizontal angles subtended by the visual display (Steinicke et al., 2011) is believed to influence a variety of aspects of human performance and perception, including, but not limited to, navigation performance in real and virtual environments (Hassan, Hicks, Lei, & Turano, 2007; Jansen, Toet, & Delleman, 2010; Toet, Jansen, & Delleman, 2007), self-motion perception (Nilsson, Serafin, & Nordahl, 2014), postural stability (Duh, Lin, Kenyon, Parker, & Furness, 2001), reaching distance estimation (Watt, Bradshaw, & Rushton, 2000), as well as simulator sickness (Lin, Duh, Parker, Abi-Rached, & Furness, 2002). and intellectual challenges that, in turn, help determine whether challenge-based immersion is experienced. Alternately, this implies that system immersion may influence the experience of challenge-based immersion. Table 4 summarizes the definitions of immersion pertaining to a bout by the experience of challenges requiring mental or sensorimotor skills. Table 4. Immersion as a Reaction to Challenges in Terms of Form, Content, and User Response. Terms Form Content User response Challengebased immersion (Ermi & Mäyrä, 2005) While the effects of form are not explicitly addressed by the authors, it seems likely that it may be influential (e.g., whether practice is necessary in order to use the controls or displays). Results from confrontations with nontrivial challenges that for action. Intense and focused attention on the challenge at hand. Strategic immersion (Adams & Rollings, 2006) It is possible that form may be influential (e.g., the type of visual display may influence challenges involving spatial perception, such as navigation tasks). Results from challenges intellect. Intense and focused attention on an intellectual challenge. Tactical immersion (Adams & Rollings, 2006) It is possible that form may be influential (e.g., the precision and complexity of the peripherals may influence performance). Results from challenges sensorimotor skills. Intense and focused attention on evaluation of occurring obstacles and responding with appropriate actions. Immersion Revisited 123 Figure 3. Illustration of how the different types of immersion may elicit a sensation of presence following E. L experience. The grey circles represent instances believed to elicit presence. The three axes represent the extent to which interaction with a system involves system immersion (vertical), narrative immersion (horizontal), and challenge-based immersion (depth). The degree to which each type of immersion is presented is represented on a scale from 0 to 1, where 0 represent absence and 1 represents the highest possible level of immersion. entirely on reacting to obstacles represented within the environment, which implies that the attentional resources are almost entirely devoted to direct perceptual processing (Circle C, Figure 3). Layers of Presence Riva and colleagues have proposed that the sensation of presence within real and virtual environments can be described in terms of layers of presence (Riva, 2009; Riva et al., 2004; Riva, Waterworth, Waterworth, & Mantovani, 2011). This proposition can be viewed in some capacity as an extension of E. L. experiences in terms of the focus, locus, and sensus of attention. To be exact, it helps explain how focus might shift to produce a state of either presence or absence (Riva et al., 2004). Riva et al. (2004) described presence as a bio-cultural mechanism that has evolved to help the self-making sense of perceived sensory data. Thus, presence may be the feeling that makes it possible for an individual to separate external percepts from internal mental constructions composed of imagined events and situations (Riva et al., 2004). The authors argued that, despite being experienced as a unitary feeling, it is possible to distinguish between three separate layers of presence associated with each of the three levels of the self, as proposed by Damasio (1999). In addition to drawing on the work of Damasio (1999), the Nilsson, Nordahl, & Serafin 124 notions core consciousness and extended consciousness (2004) environment. Core consciousness essentially refers to the basic integrated representation of the current environment. This level of consciousness may be shared across many species and be independent of language, reasoning, and memory (Riva et al., 2004). Extended consciousness is believed to rely largely on working memory and enables the individual to form and attend to internal worlds. Also, it makes it possible for the individual to consider possibilities extending beyond the current external situation (Riva et al., 2004). The three layers of presence proposed by Riva et al. (2004) are proto presence,core presence, and extended presence. Proto presence is viewed as a mostly unconscious embodied presence that helps distinguish the self from the nonself through the coupling of perception and action. Thus, proto presence relies heavily on kinesthetic information about the relative position of the body in space. A high level of coupling between performed movements and perceptions will result in a large degree of differentiation between the self and the surrounding environment. The second layer, core presence, is described as the process of selective attention performed by the self on perceptions. When a large degree of attention is assigned to sensorial experiences, other neural processes are left in the background, leaving room for identification of the present moment and the tasks at hand. Finally, extended presence helps establish the significance of external events with respect to the self and thereby helps ensure that the self is present in significant experiences. When the three layers are integrated and leveled at a particular situation, this may give rise to what Riva et al. (2004) refer to as proto consciousness. When the contents of proto, core, and extended consciousness are aligned, then maximal presence is experienced, that is, the outermost extreme of the focus dimension described by E. L. Waterworth and Waterworth (2001). Contrarily, the other extreme of focus (i.e., absence) may arise when the current environment occupies a very small part of extended consciousness (Riva et al., 2004). laboration on E. L. attention influence virtual experiences. Therefore, it does not come as a surprise that the relation between the two theories and the new taxonomy is similar (see Figure 3). Riva et al. (2004) argued that print media and verbal accounts primarily engage extended consciousness and are unable to produce core or proto presence. For that reason, the integration of the three layers of presence is limited. Media forms relying more heavily on visual imagery, such as photographs or film, may to a larger extent elicit core presence. However, given their inability to support (2004) theory of presence suggested that a relatively high degree of system immersion may be a prerequisite for a maximal experience of presence within VR. In order for all three layers to be integrated, it is necessary to elicit proto presence, which is said to function on the level of proprioception, and spatial and internal monitoring (Riva et al., 2004). Considering that high levels of system immersion will enable the user to naturally perceive and interact within a computer-generated environment, such systems should support proto presence. However, it would seem that system immersion will not always suffice because the integration of all three layers is important for maximal presence. To elaborate, extended presence requires content that is either emotionally or intellectually significant. Thus, a virtual environment devoid of significant contents will be less likely to elicit a strong sensation of presence. Both narrative Immersion Revisited 125 immersion and challenge-based immersion are arguably accompanied by extended presence because an individual experiencing these types of immersion, by definition, is mentally absorbed by the unfolding narrative or the obstacles within the environment. As it happens, Riva et al. (2004) highlighted that narratives may be crucial when one wishes to design for optimal presence. However, they stressed that, in order for narratives to positively influence the sensation of presence, the user will have to assume the role of a character and inhabit the story. Similarly, the authors suggested that maximal presence bears semblance to the concept of flow. The characteristics of a flow state include intense and focused attention and a merging of action and awareness. Similarly, maximal presence may be experienced when proto, core, and extended consciousness are leveled at the same external event. Because challenge-based immersion in many regards corresponds to the state of flow, it seems likely that this form of immersion also would be conductive to presence as it is described by Riva et al. (2004). Immersion and Illusions of Place and Plausibility Slater and colleagues described presence as the phenomena occurring when individuals respond to virtual stimuli in the same way as they would when exposed to equivalent unmediated stimuli (Sanchez-Vives & Slater, 2005; Slater, Lotto, Arnold, & Sánchez-Vives, 2009). More behaviors, through automatic reactions, conscious volitional behaviors, through to cognitive processing -Vives & Slater, 2005, p. 338). Thus, the sensation of presence makes up the subjective experience of a realistic response to virtually generated stimuli, that is, a response that would be identical if the stimuli were the sensation of being there is not the sole factor in determining whether an individual responds realistically to virtual stimuli (Rovira, Swapp, Spanlang, & Slater, 2009; Slater, 2009). Slater (2009) presented the hypothesis that this response-as-if-real can be ascribed to the simultaneous occurrence of not one but two perceptual illusions: the place illusion the illusion that you are really there despite the sure knowledge that you are not and the plausibility illusion the illusion that the unfolding events are really happening in spite of the knowledge that they are not. Combined with notions of immersion and a virtual body, the place and plausibility illusions make up a conceptual framework for explaining how VEs potentially can transform our experience of space and ourselves (Slater, 2009). Slater (2009) reserves the term place illusion for the type of presence that refers to the qualia of being there despite knowing that one really is not. Qualia can simply be understood as relationship between the wavelength distribution of light and color perception as a metaphor to describe the connection between immersion and presence. Just as a color can be objectively described based on its wavelength distribution, so can immersion be described based on objective properties, such as frame rate, fidelity of tracking, or the size of the field of view. Even though wavelength distribution and immersion are objectively describable, they both lead to subjective experiences, namely, perceived color and illusions of place. Slater (2009) argued that one may characterize an immersive system by the sensorimotor contingencies it supports. Sensorimotor contingencies correspond to the actions that the user knows how to perform when on or Nilsson, Nordahl, & Serafin 126 taking a step forwards in order to more closely inspect an object. Slater (2009) went on to describe that the place illusion occurs as a function of the range of normal sensorimotor contingencies facilitated by the system. While system immersion is an objectively measurable quantity, presence is not. Thus, it is entirely possible for two individuals to experience different levels of presence despite being exposed to the same immersive system. The difference in experienced presence need not be caused by individual differences. Instead, a difference in the actions performed by the two individuals might be responsible for the variations in the sensations of presence. One person might explore the environment to a larger extent than the other: for example, by picking up and inspecting objects and thereby testing the limits of the and existing definitions of immersion (e.g., general definition of immersion, Witmer & Singer, 1998; perceptual immersion, McMahan, 2003; and sensory immersion, Ermi & Mäyrä, 2005). In other words, these definitions hold that immersion corresponds to the subjective sensation of -fidelity tracking and displays. For that reason, it may not be particularly fruitful to rely on these definitions of immersion following this view of presence (Slater 1999). Unlike place illusion, plausibility illusion is not the direct result of an individ to perceive the VE. Instead, this perceptual illusion arises as a result of what the individual perceives within the environment. Specifically, the plausibility illusion occurs when the unfolding events are experienced as actually occurring, despite the certain knowledge that they are not (Slater, 2009). Rovira et al. (2009) indicated that the plausibility illusion depends on the VE meeting at least three conditions: (a) The actions performed by the user must produce correlated reactions within the VE (e.g., a virtual character might avoid eye contact and step aside if the user stares or exhibits aggressive body language); (b) The environment should respond directly to the user, even when the user is not performing an instigating action (e.g., a virtual character might react to the presence of the user without the user initially approaching or addressing this character); and (c) The environment and the events occurring ledge and expectations accrued through a lifetime of unmediated interactions. (1997) distinguished between two forms of realism that may contribute to the experience of presence, whether perceived in isolation or in concert, namely social realism and perceptual realism. Perceptual realism refers to the extent to which mediated artifacts appear like their real-world counterparts; (Lombard & contingent upon visual realism (Sanchez-Vives & Slater, 2005), plausibility illusion shares some commonalities with social realism. Slater (2009) described the body as the focal point where the illusions of place and plausibility are fused. During everyday interactions within unmediated environments, we humans continuously receive sensory information about our bodies. Slater (2009) argued that this ability to perceive ourselves serves as a strong confirmation of the place illusion. That is to say, if we are able to perceive our body then we must be there. The ability to provide users of VEs with a credible virtual body is therefore central to eliciting illusions of place. Immersion Revisited 127 On the topic of the relationship betwe outlined earlier in this paper, it is evident that system immersion is viewed as the principal determinant for compelling place illusions (the circle labeled A in Figure 4). That is, the place illusion should increase as the range of natural sensorimotor contingencies supported by the system increases. Consequently, it may seem puzzling that individuals report experiencing a sense of being there after engaging with lower order immersive systems, such as a first-person video game played on a desktop system. When attempting to explain this predicament, Slater (2009) hypothesized that the types of presence brought about by lower and higher order immersive systems are qualitatively different. The illusion of being there elicited by systems providing a high level of system immersion happens as a consequence of exposure to the sensory stimuli. Contrarily, Slater (2009) provided the following account of the experience accompanying desktop systems: In the case of a desktop system the situation is quite different; the feeling reported as being there if it comes at all is after much greater exposure, requires deliberate attention and is not automatic it is not simply a function of how the perceptual system normally works, but is something that essentially needs to be learned, and may be regarded as more complex. (Slater, 2009, p. 3552). Some of Slater and colleagues early work on walking-in-place locomotion arguably lend some credence to this claim. Slater, Usoh, and Steed (1995) found that the subjective sensation of presence was higher on behalf of subjects walking in place rather than pressing a button to Figure 4. Illustration of how the different types of immersion may elicit a sensation of presence following presence. The three axes represent the extent to which interaction with a system involves system immersion (vertical), narrative immersion (horizontal), and challenge-based immersion (depth). The degree to which each type of immersion is presented is represented on a scale from 0 to 1, where 0 represent absence and 1 represents the highest possible level of immersion. Nilsson, Nordahl, & Serafin 128 generate virtual movement. Usoh et al. (1999) confirmed these findings and also found that real walking is better than the two other input methods in terms of simplicity, straightforwardness, and natu may elicit stronger illusions of place than lower order systems, it would seem that players may exhibit emotional responses similar to those experienced in real life when interacting with lower order immersive systems. One example is the emotions experienced by phobic patients who play video games as treatment for their phobias (Bouchard, Côté, St-Jacques, Robillard, & Renaud, 2006). subcategories (temporal, spatial, and emotional) appear to have no effect on the place illusion. These forms of immersion are characterized by the user becoming mentally absorbed by the attraction toward, or aversion to, the sight, sound, and feeling of the virtual world is obviously relevant to the study of user experiences of VEs. However, these are matters of content rather than form, and they are therefore deemed inconsequential for the experience of presence following this view. To borrow an example from Slater (2003), imagine listening to a live Toccata and Fugue in D minor on a high-end surround system. You do not need to be a classical music aficionado to experience the sensation of being in the concert hall. However, if you favor heavy metal, it is unlikely that you will find a similar situational experience enjoyable or involving. Thus, it would seem that narrative immersion should not be considered a factor contributing to illusions of place as described by Slater (2009). Finally, it is unlikely that challenge-based immersion is a factor influencing the place illusion, as introduced by Slater (2009). While the experience of challenge-based immersion will entail allocation of attention to the virtual obstacles, this does not mean that presence is experienced. As in real life, one may find a particular virtual task boring, enjoyable, or aggravating due to its difficulty level, but that has nothing to do with whether one feels present or not. This being said, one may argue that there might be one way in which narratives and challenges indirectly can influence the place illusion. Because the extent to which users probe the bounds of the immersive system might influence presence, it seems possible that the risk of too close inspection can be reduced by means of narrative contents and challenges explicitly designed to discourage users from performing undesired actions. IMPLICATIONS FOR RESEARCH OR APPLICATION The general aim of our research has been to explicate the different meanings associated with the term immersion and to clarify how these relate to varying views of presence. A better understanding of the similarities and differences between theories of presence and immersion may have implications for how scholars and researchers approach the study of these areas and for developers who seek to elicit and evaluate such experiences. The current ambiguous and interchangeable use of terminology related to immersion and presence in the literature often results in a mismatch between the phenomena scholars wish to study and the methods they end up employing. For example, one theory of immersion or presence is taken as a point of departure but, in the data collection and/or analysis, the employed metrics are devised based on a different view of the concepts. Thus, clarified Immersion Revisited 129 knowledge of the theories pertaining to immersion and presence will help students, researchers, and developers to make well-informed decisions when consulting the literature, and thereby ensure correspondence between the theoretical underpinnings of a given project, design decisions, and the employed evaluation method. Specifically, the proposed taxonomy offers a useful starting point for both individuals who are entirely new to the concepts immersion and presence, and individuals that are just familiar with how the terms are used in a specific domain (e.g., video game studies or VE research). This is particularly relevant considering that technologically immersive virtual reality is becoming increasingly widespread and video games are a primary application area of such technology. Thus, game researchers are increasingly likely to need an understanding of the theory familiar to researchers working with VEs and vice versa. Moreover, immersive technologies are also being adopted by researchers and developers working within a variety of different fields, including health care and education, and the work documented in the current paper will serve as a valuable introduction to such individuals. Finally, because we propose that the different views on the concepts immersion and presence each have their merits, our work may help inform potential future research questions on behalf of scholars studying both video games and VEs: For instance, how does system immersion influence challenge-based and narrative immersion, and how can narrative elements and challenges be used to subtly prevent the user from probing the bounds of the system in a manner that disrupts the sensation of presence. CONCLUSIONS Through the research documented in the current paper, we sought to address two primary questions: What meanings are associated with the term immersion and how do these meanings map onto existing views of presence? In order to address these questions, we presented a review of existing definitions of immersion related to VEs, video games, and literary works of fiction and, based on this review, a taxonomy of different conceptualizations of immersion was proposed. Specifically, this taxonomy organizes existing definitions of immersion along three orthogonal dimensions: (a) immersion as a property of the system, (b) immersion as a response to an unfolding narrative, the diegetic space, or virtual characters, and (c) immersion as a intellect or sensorimotor skills. The first is an objectively measurable property of the system whereas the last two are characterized by an experience of intense and focused attention on events in the virtual world. Most existing categorizations of immersion are aligned with one of these two descriptions; that is, immersion is either an objective property of the system or a subjective state of the user. The proposed taxonomy illustrates that such dissimilar views need not be a source of ambiguity, but rather exactly because most existing views of immersion have their merits that researchers and developers need to clearly specify what they mean when using the term immersion. Taxonomies such as the one proposed in this paper should make this task easier. The four theories of presence outlined in the current paper all relate to the sensation of being in a given virtual (or unmediated) environment. However, they differ in terms of the factors believed to influence presence. Particularly, the theories differ in regard to the importance assigned to mental imagery and the degree of explicit attention assigned to the sensory stimuli Nilsson, Nordahl, & Serafin 130 depicting the environment. Biocca (2003) did not view system immersion to be a prerequisite for the illusion of being there because presence is dependent on a mental model of space that can receive spatial cues from sources other than sensory perception. Thus, following this view, narrative immersion should positively influence the sensation of presence. Moreover, challengebased immersion may positively influence presence on behalf of users exposed to higher levels the virtual world. The theories proposed by E. L. Waterworth and Waterworth (2001) and Riva et al. (2004) assigned greater importance to system immersion because the sensation of presence is thought to be contingent upon information being processed directly by the perceptual motor systems. Notably, it would seem that narrative immersion may positively influence the sensation of presence as described by both E. L. Waterworth and Waterworth (2001) and Riva et al. (2004). Narrative immersion entails intense and focused attention on the unfolding narrative events. Such attention should reduce the risk that users will engage in mental acts involving conceptual processing that takes away resources from the direct perceptual processing necessary for presence (J. A. Waterworth & Waterworth, 2003). Similarly, narrative immersion may influence presence as described by Riva et al. (2004) because emotionally or intellectually significant events may induce extended presence. Challenge-based immersion brought about by sensorimotor challenges may also indirectly influence the sensation of presence following the theories of Waterworth and Waterworth (2001) and Riva et al. (2004) because it involves allocation of attention to the events occurring within the environment.Finally, Slater (2009) argued that the sensation of being there within a VE (i.e., the place illusion) occurs as a function of the range of normal actions the user knows how to perform when attempting to perceive. Based on this account, it is apparent that system immersion is viewed as the principal factor determining whether presence is experienced. Nevertheless, this does not mean that the place illusion is viewed as being the same as system immersion. One user may perform actions that the system does not support, thus experiencing a different degree of the illusion than a user who does not probe the bounds of the system. Moreover, the narrative contents or the posed challenges may indirectly influence the place illusion by encouraging the user only to perform actions permitted by the system. Neither narrative immersion nor challenge-based immersion should be influential. Following this view, the illusion of place appears to be divorced from the li may be characterized equally well by indifference and excitement. Just as in real life, a user may find virtual events irrelevant, fascinating, challenging, or trivial, but that has nothing to do with whether the place illusion is experienced. In this paper, we have attempted to highlight the relatively large differences between existing views of what characterizes and causes presence. We believe it to be crucial that researchers and developers are mindful of these differences when interpreting the findings of others and when selecting what measures of presence to employ. Furthermore, because the terms presence and immersion have been used to refer to similar phenomena, a number of the methods developed to study some conceptualizations of presence may be applicable when studying psychological immersion and vice versa. In particular, both narrative and challengebased immersion are characterized by an experience of intense and focused attention on events in the virtual world. Similarly, some views of presence hold that the sense of being in the assessing presences in terms of allocation of attentional resources should also be applicable Immersion Revisited 131 when attempting to assess the degree to which narratives or challenges fully attention. To exemplify, IJsselsteijn, de Ridder, Freeman, and Avons (2000) described that the so-called secondary reaction time measure has been used to measure presence. The underlying assumption is that the user will react slower and produce more errors on a given secondary task, as compared to the primary task, if presence is experienced. Because such methods essentially operationalize presence in terms of allocation of attentional resources, they may also be used to assess the intensity of narrative and challenge-based immersion. Thus, knowledge of the differences and similarities between varying views of immersion and presence will enable students, researchers, and developers to make well-informed decisions when consulting the literature in search for design guidelines and evaluations methods. Even though the current paper does provide an overview of existing views of immersion and their relation to four theories of presence, it is possible to point to certain limitations of the work and propose potential directions for future research. Most notably, the literature review is not exhaustive, and therefore we cannot claim that all conceptualizations of immersion and presence have been covered. For that reason it would be meaningful for future work to adopt an approach similar to the one employed when performing critical reviews (Cook et al., 1997). That is, such a review should involve a comprehensive search of all potentially relevant work based on reproducible criteria. Other than providing a more complete picture, a critical review would also enable researchers to comment on the prevalence of various definitions of the terms across different domains and allow for the work to include a systematic review of the design principles and evaluation methods associated with different conceptualizations of immersion and presence. Moreover, it would be meaningful for future work to more explicitly include related terms such as engagement, absorption and involvement. Nevertheless, it is hard to argue why the term immersion is better suited to describe certain notions rather than others. Thus, we hope that the current review and the accompanying the taxonomy may offer clarity by making explicit the different conceptions of the term immersion and their relation to different theories of presence. REFERENCES Adams E., & Rollings A. (2006). Fundamentals of game design. Upper Saddle River, NJ, USA: Prentice Hall, Upper Saddle. Argyle, M., & Dean, J. (1965). Eye-contact, distance and affiliation. Sociometry,28(3), 289 304. Arsenault, D. (2005). Dark waters: Spotlight on immersion. In proceedings of the Game-On North America 2005 Conference (pp. 50 52). Ghent, Belgium: Eurosis. Biocca, F. (2003, May). Can we resolve the book, the physical reality, and the dream state problems? From the two-pole to a three-pole model of shifts in presence. Paper presented at the EU Future and Emerging Technologies, Presence Initiative Meeting, Venice, Italy. Retrieved June 17, 2016, from http://www.mindlab.org/images/d/DOC705.pdf Blascovich, J., & Bailenson, J. (2011). Infinite reality: Avatars, eternal life, new worlds, and the dawn of the virtual revolution. New York, NY, USA: HarperCollins Publishers. Bouchard, S., Côté, S., St-Jacques, J., Robillard, G., & Renaud, P. (2006). Effectiveness of virtual reality exposure in the treatment of arachnophobia using 3D games. Technology and Health Care,14(1), 19 27. Brown, E., & Cairns, P. (2004). A grounded investigation of game immersion. In CHI'04 extended abstracts on human factors in computing systems (pp. 1297 1300). New York, NY, USA: ACM. Nilsson, Nordahl, & Serafin 132 Chen, J. (2007). Flow in games (and everything else). Communications of the ACM,50(4), 31 34. Cook, D. J., Mulrow, C. D., & Haynes, R. B. (1997). Systematic reviews: Synthesis of best evidence for clinical decisions. Annals of Internal Medicine,126(5), 376 380. Csikszentmihalyi, M. (1990). Flow: The psychology of optimal experience. New York, NY, USA: Harper & Row. Damasio, A. (1999). The feeling of what happens: Body, emotion and the making of consciousness. San Diego, CA, USA: Harcourt Incorporated. Dennett, D. C. (1988). Quining qualia. In A. Marcel & E. Bisiach (Eds.), Consciousness in modern science. Oxford, UK: Oxford University Press. Duh, H. B. L., Lin, J. J., Kenyon, R. V., Parker, D. E., & Furness, T. A. (2001, March). Effects of field of view on balance in an immersive environment. Paper presented at the 2001 IEEE Virtual Reality Conference, Yokohama, Japan. Dura, M. T. (2006). The phenomenology of the music-listening experience. Arts Education Policy Review, 107(3), 25 32. Ermi, L., & Mäyrä, F. (2005). Fundamental components of the gameplay experience: Analysing immersion. In S. D. de Castell & J. Jenson (Eds.), Worlds in play: International perspectives on digital games research (pp. 15 27). New York, NY, USA: Peter Lang Publishing. Fox, E. (2008). Emotion science cognitive and neuroscientific approaches to understanding human emotions. Basingstoke, UK: Palgrave Macmillan. Hassan, S. E., Hicks, J. C., Lei, H., & Turano, K. A. (2007). What is the minimum field of view required for efficient navigation? Vision research,47(16), 2115 2123. Ihde, D. (2007). Listening and voice: A phenomenology of sound (2nd ed.). New York, NY, USA: State University of New York Press. IJsselsteijn, W. A., de Ridder, H., Freeman, J., & Avons, S. E. (2000, June). Presence: concept, determinants, and measurement. Paper presented at Human Vision and Electronic Imaging V conference, San Jose, CA, USA. International Society for Presence Research (ISPR). (2000). The concept of presence: Explication statement. Retrieved June 17, 2016, from https://ispr.info/about-presence-2/about-presence/ Jansen, S., Toet, A., & Delleman, N. (2010). Restricting the vertical and horizontal extent of the field-of-view: Effects on manoeuvring performance. The Ergonomics Open Journal,3, 19 24. Kosslyn, S. M. (1983). . New York, NY, USA: W. W. Norton. Kosslyn, S. M. (1996). Image and brain: The resolution of the imagery debate. Cambridge, MA, USA: MIT Press. Kosslyn, S. M., & Koenig, O. (1992). Wet mind: The new cognitive neuroscience. New York, NY, USA: Free Press. Lin, J. J. W., Duh, H. B., Parker, D. E., Abi-Rached, H., & Furness, T. A. (2002, March). Effects of field of view on presence, enjoyment, memory, and simulator sickness in a virtual environment. Paper presented at the 2002 IEEE Virtual Reality Conference, Orlando, Florida, USA. Lombard, M., & Ditton, T. (1997). At the heart of it all: The concept of presence. Journal of Computer Mediated Communication,3(2), unpaginated. doi: 10.1111/j.1083-6101.1997.tb00072.x/ McMahan, A. (2003). Immersion, engagement, and presence: A method for analyzing 3-D video games. In W. Mark & B. Perron (Eds.), The video game theory reader (pp. 67 86), New York, NY, USA: Routledge. Minsky, M. (1980). Telepresence. Omni,2, 45 51. Murray, J. B. (1997). Hamlet on the holodeck: The future of narrative in cyberspace. New York, NY, USA: Free Press. Nakamura, J., & Csikszentmihalyi, M. (2005). The concept of flow. In C. R. Snyder & S. J. Lopez (Eds.), Handbook of positive psychology (pp. 89 105). Oxford, UK: Oxford University Press.