Presence and the Self: a cognitive neuroscience approach
This paper proposes a neurobiology-based theory of presence based
on four different positions related to the role and structure of presence,
as follows. First, presence is a defining feature of self and it is related
to the evolution of a key feature of any central nervous system: the
embedding of sensory-referred properties into an internal functional space.
Without the emergence of the sense of presence it is impossible for the
nervous system to identify the separation between an external world and the
internal one. Second, even if the experience of the sense of presence is an
unitary feeling, conceptually it can be divided in three different layers,
phylogenetically different and strictly related to the three levels of self
identified by Damasio (Damasio, 1999).
In particular we can make conceptual distinctions between proto presence, core presence, and extended
presence. Third, given that each layer of
presence solves a particular facet of the internal/external world
separation, it is characterized by specific properties. Finally, in humans
the sense of presence is a direct function of these three layers: the more
they are able to differentiate the self from the external world, and the
more they are integrated, the more we experience a sense of presence.
neurobiology, the self, presence layers,
1 The Biological Purpose of Presence
1.1 The emergence of extended consciousness
For organisms in a natural environment, it is vital to pay
attention and respond rapidly to present threats and opportunities. Our
emotional and cognitive life is built on this evolutionary substrate. But
as our self evolved, imagined situations became increasingly important to
survival and biological success. In his Brainstorms
book, Dennett suggested the existence of an important difference between self and point of view:
view clearly had something to do with personal location, but it was itself
an unclear notion. It was obvious that the content of one's point of view
was not the same as or determined by the content of one's beliefs or
thoughts. For example, what should we say about the point of view of the
Cinerama viewer who shrieks and twists in his seat as the roller-coaster
footage overcomes his psychic distancing? Has he forgotten that he is
safely seated in the theater? Here I was inclined to say that the person is
experiencing an illusory shift in
point of view. In other cases, my inclination to call such shifts
illusory was less strong. The workers in the laboratories and plants who
handle dangerous materials by operating feedback-controlled mechanical arms
and hands undergo a shift in point of view that is crisper and more
pronounced than anything Cinerama can provoke.” (p. 314-315, Italics added)
As noted by IJsselsteijn and Riva (IJsselsteijn & Riva, 2003), what Dennett calls “an illusory shift in point of view”
conceptualizes well the concept of presence. The question is, how our mind
can say that this shift in the point of view is illusory? How is it
possible to differentiate between a real and an imagined situation?
According to recent psychological theory, perceptions are
guesses of what is out there now and predictions of what is about to
happen. A way to put this is that perceptions are rather like hypotheses of
science - predictions of unsensed features of objects, and of futures that
may not happen (Gregory, 1998b).
They are never certainly true and often wrong. Yet the guesses of
hypotheses are the nearest we ever get to reality. If perceptions are
internal predictions, how can we differentiate them from other internal
processes, such as conceptual modeling?
According to current neurobiological
work, evolution created two different levels of consciousness to solve this problem (Damasio, 1999): core consciousness and extended consciousness. Core consciousness is what we share with some nonhuman
animals - a simple biological phenomenon, the scope of which is the Here
and Now. This basic, integrated representation of one moment and one place
is independent of language, reasoning and memory (Metzinger, 1999).
When we imagine, think, plan and generally deal with information
that does not only constitute our experience of things and events in the currently
present external situation we are exercising extended consciousness: “Extended consciousness has to do with making the
organism aware of the largest possible compass of knowledge.” (p. 198).
According to Damasio, extended consciousness emerges from:
The gradual build-up of memories
of the organism’s biography (the experiences of the “core-self”). Each
autobiographical memory then becomes an object, which takes part in
inducing and enhancing core consciousness;
The ability to hold active,
simultaneously and for an extended period of time, many images that
collectively define the autobiographical self and the object it is
It is extended consciousness that allows us to create an
internal world in which we may suspend disbelief, as compared to a
perceptual world experienced as outside the self. Extended consciousness
relies on working memory (Damasio, 1999),
which can be seen as the “active scratchpad” of mental life (Baars, 1988).
It is in working memory that the internal world we are currently
experiencing is largely created. Its main function is to allow us to
consider possibilities not present in the current external situation. In
contrast, core consciousness is directed exclusively to the here and now –
the present – and is what we share with all conscious animals.
Extended consciousness gives us obvious advantages over
organisms without it, such as the ability to plan and generally enact in
the imagination possible scenarios in the future, as well as to increase
the sophistication of learning from the past. Language depends on it,
because we must retain linear sequences of symbols in working memory if we
are to understand utterances, whether spoken or written.
The advantages of extended consciousness depend on the fact that
we can distinguish between the experience of the external word and
experience of internal worlds, both remembered and imagined. Confusions of
the two indicate serious psychological problems, problems which, until
recent times, would have prevented survival and the passing on of this
condition. As noted by Waterworth and Waterworth (Waterworth & Waterworth, 2003): “if we react as if the external world is only imaginary we
will not survive long (think of this the next time you cross a busy street).
And if we think that what we are merely imagining is actually happening, we
may omit to carry out basic activities on which our survival depends. We
are suggesting that presence is the feeling that evolution has given us to
make this vital distinction.” (p. 2)
1.2 The presence of self
According to this view, what is the role of self? Damasio proposes important conceptual distinctions
between a preconscious precedent of self and two distinct notions of
self-consciousness (Damasio, 1999; Dolan, 1999):
- the proto self:
a coherent collection of neural patterns that map, moment by moment,
the physical state of the organism;
- the core self:
a transient entity which is continuously generated through encounters
- the autobiographical
self: a systematic record of the more invariant properties that the
organism has discovered about itself.
In this vision, the basis for a conscious self is a feeling
state that arises when organisms represent a non-conscious proto-self in
the process of being modified by objects. In essence, the sense of self
depends on the creation of a second-order mapping, in certain brain regions
(brainstem nuclei, hypothalamus, medial forebrain
and insular and somatosensory cortices), of how the proto-self has
been altered (Dolan, 1999).
However, it is only the autobiographical self that generates the
subjective experience of possessing a transtemporal identity. The presence of the
autobiographical self centers the flow of our interactions with perceptual
objects on itself, thereby making them our own experiences. In summary, the
presence of you is the feeling of
what happens when your being is modified by the acts of apprehending
something (Metzinger, 1999).
1.3 The brain mapping
As we have just seen, core self and
core consciousness have their origins in a mapping of body states and are
about two facts: the organism relating to sensory streams and the fact that
this relation causes a change in the organism. It follows that a key
starting point for a theory of presence is description of how the brain
maps its sensorial inputs, and, most importantly, the dynamics of their
Damasio tries to answer this question by adding two more components to his model:
Autobiographical Memory: the
organized record of the main aspects of our biographies;
Dispositions: records, which are
dormant in our memory until activated by a similar or related experience.
To understand how these components are related we can use an
example: the way our self experiences the first view of the Colosseum in
Rome. We receive sensory signals from our eyes, ears, nose and sense of
touch that are mapped by the proto self. Some microseconds later, this
activity is monitored by the core self and becomes the content of core
consciousness. A few microseconds more are required for the activation of
extended consciousness. Some milliseconds later, it adds dispositional
records of that place (or similar places) coming from autobiographical
memory. We may recognize the place because we studied it in architectural
history; and we may have emotional ties because we associate the place with
special memories (our most recent experience of the Colosseum was while
watching a preferred movie: “Gladiator”). The result is a single conscious
experience integrating perceptions, emotions and feeling. Once the event
has ended, it is restored in dispositional space with new data about our
most recent experience.
2 The Three Layers of Presence
One of the main ideas expressed in this paper is the link
between presence and self. More in detail, we suppose that presence is the
result of the evolution of the central nervous system in its attempt to
embed the sensory-referred properties into an internal functional space (Llinás, 2001).
As noted by Waterworth and Waterworth (Waterworth & Waterworth, 2003), the appearance of the sense of presence allows the nervous
system to solve a key problem for its survival: how to differentiate
between internal and external states.
We hypothesize that it is possible to associate
a specific layer of presence with each of the three levels of self
identified by Damasio. Further, given that each layer of presence solves a
peculiar facet of the internal/external world separation, it is
characterized by specific properties.
2.1 The first layer: proto presence
As we have seen, the main activity of the proto self is a
non-conscious mapping of the physical state of the organism. What is the
evolutionary goal of the proto self? To predict the characteristics of the
external world as it is experienced through sensorial inputs.
As suggested by Llinás this can be done even by a lamprey (Llinás, 2001).
How? The steps identify by the latest neurobiological studies are (pp.
the comparison of the sensory
referred properties of the external world with a separate internal
sensorimotor representation of those properties;
the transformation/utilization of
this premotor solution into finely timed and executed movements.
In this process movement plays a key role. On one side, an
adaptive movement is the evolutionary goal of the proto self. On the other
side, it is through motility that it can embed the propriety of the
external world in its sensorimotor representation. These properties are the
constraints generated by the coordinate systems that describe the body: in
an evolutionary process that required millions of years the proto self
experienced, through movement, these constraints and used them to model the
external world. In this vision how can we define proto presence?
Tentatively we can say that the more the proto self is in the body, the
more it is different from the external world. More precisely we can define proto presence as an embodied presence related to the level
of perception-action coupling: the more the organism is able to couple
correctly perceptions and movements, the more it differentiates itself from
the external world, thus increasing its probability of surviving.
2.2 The second layer: core presence
In Damasio's model, the second level of self is the core self, a transient entity, ceaselessly re-created for each and
every object with which the brain interacts. What is the
evolutionary goal of the core self? It is the integration of specific
sensory occurrences into single percepts.
According to Gregory (Gregory, 1998b)
this is done through a coherent world-model that evolves in real time
according to its own internal logic. In such a
vision, perception depends very largely on knowledge derived from past
experience of the individual and from evolutionary experience.
During waking consciousness, this model is modulated by the
senses, but it persists even when sensory input is temporarily cut off:
close your eyes and you'll still be keenly aware that the Colosseum is in
front of you. As far as your inner model is concerned, the Colosseum is
still there; and as that inner model is used to generate motor commands,
any movements you choose to make (such as searching for a taxi) will be
adjusted to take the Colosseum’s presence into account. As suggested by
Farber, the core self has two functional states (Farber, 2001):
while 'online' — actively synchronized with the external world — it can be
used to predict what will happen next or what the likely outcomes of
different actions will be, and while 'offline', it can model scenarios from
memory or imagination, or generate the realistic (if disordered) worlds of
our dreams. However, this model works if the nervous system is able to
differentiate between the two states. In fact,
recognizing the present is
essential for survival in the here and now.
Gregory underlined (Gregory, 1998a):
“As perception depends on rich knowledge from the past stored in the brain,
there must be a problem in identifying the present moment from past
memories, and also from anticipations running into the future. The present
is signaled by real time stimuli from the senses; but as perceptions are
90% or more stored knowledge, the
present moment needs to be identified for behavior to be appropriate to
what is happening out there now.” (p. 1694, italics added)
How is this done? Neurobiological research suggests the
existence of two specific processes: cognitive
binding and temporal coherence: In Llinás' approach (Llinás, 2001)
cognitive binding is done by the core self through the temporal linking of
the independently operating neural mechanism included in the proto self. By
inducing temporal coherence to different neural structures, the core self
is able to produce a shift in attentional focus. This shift is also able to
differentiate between dreaming and waking: in dreaming the intrinsic activity of the proto self
does not correlate sensory inputs with ongoing thalamocortical activity
(thalamocortical system is considered the site of the core self) making
them invisible to the core self (Llinás & Pare, 1991).
In these processes what is the role of core presence? Core
presence is the activity of selective
attention made by the self on perceptions: the more the organism is
able to focus on its sensorial experience by leaving in the background the
remaining neural processes, the more it is able to identify the present
moment and its current tasks, increasing its probability of surviving.
2.3 The third layer: extended presence
The higher level of self in Damasio's theory is the
autobiographical self. Autobiographical self is based both on memory and on
anticipations of the future, and integrates
memories of past experiences, learned ideas, beliefs and skills, and hopes
for the future into present experience. As detailed by Damasio (Damasio, 1999),
“autobiographical self depends on systematized memories of situations in
which core consciousness was involved in the knowing of the most invariant
characteristics of an organism's life - who you were born to, where, when,
your likes and dislikes, the way you usually react to a problem or a
conflict, your name, and so on.” (p. 86)
This involves the
use of the centers of higher thought in the
cortex and the widely distributed faculty of memory. In fact, it
develops gradually throughout life and is largely the product of adding
abilities, reasoning and memories of all the richness of experience to core
The possibility of defining internal goals and tracking their
achievement is the element that allows the final shift in the evolution of
the self: from meaning-as-comprehensibility to
meaning-as-significance. Meaning-as-comprehensibility refers to the extent
to which the event fits with our view of the world (for example, as just,
controllable, and nonrandom) whereas meaning-as-significance refers to the
value or worth of the event for us (Janoff-Bulman & Frantz, 1997). In this vision, the role of extended presence is to verify the significance of the
experience for the self. The more the self is present in significant
experiences, the more it will be able to reach its goals, increasing its
possibility of surviving.
3 Focused Presence: integrating the three layers
3.1 Focus, locus and sensus
Waterworth and Waterworth (Waterworth &
outlined a three-dimensional model of experience in relation to presence,
consisting of focus, locus and sensus. Principally, the model was intended to provide a
possible design space, in which potential and actual interactive media
applications could be placed, as an aid to both design and evaluation. Focus described the nature of an
observer’s attention, specifically whether attention is mostly directed
towards present events (in the real or a virtual world) – in which case the
models predicts a high degree of presence – or is mostly directed towards
internally-generated information which is not currently present in the
world. The former can be characterised as perceptual (or concrete)
processing, the latter as conceptual (or more abstract) processing.
Waterworth and Waterworth (Waterworth &
referred to this latter, reflective state of mind as absence, corresponding to a low degree of presence, and suggested that position on the focus dimension determines the degree
of experienced presence.
We can now extend and refine this concept of focus in light of the three levels
of presence proposed earlier in the paper. Specifically, we suggest that focus can be seen as the degree to
which the three layers of presence are integrated towards a particular
situation. The more integrated the layers, the higher the degree of
experienced presence. Presence would be maximized when the contents of
extended consciousness are closely aligned to those of core consciousness
and of proto consciousness, when the three levels are working in concert to
produce a strong focus on the present environment. The pivot for this
integration is core presence. Absence of mind thus arises when extended
consciousness is minimally concerned with the current situation, or
situations, with which core consciousness is involved.
From a biological, survival perspective, the real world
has priority and is the background against which mental life is framed. The
proto self exists moment by moment through our monitoring of our internal
and external environment. To maintain our bodies in the world we need to
know both their internal state and their precise relations to the world
immediately around them. Much of this is unconscious and automatic, we only
become specifically aware of processes such as digestion or proprioception
when things do not function normally, within limits acceptable for the
stability of the organism. This awareness arises as the events are
integrated into core consciousness, as described earlier.
One of the main reasons for current interest in presence
is that it may be evoked by both the real world and by media. The locus dimension (Waterworth &
captures the extent to which the observer is attending to the real world or
to a world conveyed through media. The biological purpose of presence means
that it is dominated by the current state of the body, and perceptions of
the current state and position of the body in relation to the world in
which the body is located. Any mediated presence is in competition with
presence in the real world. "Breaks in presence" (Slater & Steed,
are an example of rapid shifts of presence between the real and a mediated
world. In other words, they seem to be temporary changes in the locus of experience, although
Spagnolli and Gamberini (2002) present evidence that
they are more a temporarily wider distribution of presence over the locus
dimension – taking in both the real and the virtual worlds.
The history of media and their effects is complex and
beyond the scope of this paper. We will simplify for present purposes by
suggesting that some traditional non-electronic media, such as books,
verbal accounts, and letters, address extended consciousness. This limited
capability was mirrored later by electronic media such as text documents,
e-mails and telephone calls. All of these produce a conceptual model in the
reader or hearer that is usually not closely or immediately related to his
or her current situation in the real world. In other words, they do not
elicit core or proto presence. Because of this, they produce a relatively
low degree of presence integration and are low on the focus dimension. Traditional pictorial media forms such as
drama, painting and sculpture were often successful in evoking a sense of
core presence and sometimes also a sense of extended presence with which it
was integrated to a greater or lesser degree. Again, this is mirrored by
more recent electronic media such as television, computer graphics, and
animations. Still, not all levels of presence are addressed by such media
and, because of this inherently restricted focus, the degree of experienced presence is correspondingly
The third dimension of Waterworth and Waterworth’s (Waterworth & Waterworth, 2001) model, sensus, refers to the level of
consciousness or attentional arousal of the observer, and we can also
interpret its effects on presence in terms of our three layers of presence.
Arousal will affect such factors as degree of activity of the organism, and
the effect is likely to be passed upwards, to the core self, which may then
become more actively engaged in the world. Conversely, arousal of the core
layer will tend to impact downwards on the proto self, which will become
innervated to cope efficiently with the current situation. At the level of
extended consciousness, attentional arousal will tend to be determined by
the significance of what is experienced, the meaning of current events.
3.2 Presence in media: limitations and potentials of designed presence
In this section, we apply our three-layer theory of presence to
try to understand the different ways in which aspects of mediated
experience impact on presence. From that, we outline the potential of this
view as a tool for designing particular types of experience with
predictable degrees and types of presence.
Because we are always in the real world, even when engrossed in
media or in thought, proto presence is probably never totally divorced from
the current physical situation and state in which we find ourselves. Most
mediated experiences do not attempt to address the individual at the level
of proto consciousness, since the technical demands of eliciting presence
are less the higher the layer invoked. As already stated, absence of mind
arises when extended consciousness is minimally concerned with the current
situation, or situations, with which the other two layers are involved. A
well-written novel can readily engage extended consciousness, while core
consciousness will be little affected, and proto consciousness not at all.
Overall, presence is not focused, and the degree of reported presence will
be relatively low. Some researchers suggest that a novel may provide the
technological minimum for presence in media (e.g. Slater, 2003). Since we
view presence as a solution to the problem of determining what is happening
to the self at the present time, we suggest that extended presence does not
exist without core consciousness. Core consciousness drives the problem
solution; the more it is able to integrate the three layers, the more
convincing the answer to the problem.
Moving down from extended to core consciousness, the
technological demands on the medium increase. Whereas the machinery of
conceptual modeling is abstract and relatively slow, perceptual models and
the predictions they provide must be created fast, since this core level is
evolutionarily designed to support what may be very rapid interactions with
the real world. To mimic this natural interactivity involves rapid response
times between a medium and its user, and often involves detailed
inspectability of aspects of any displayed information. More generally,
information must be displayed in concrete forms that can be accepted by
core consciousness as realistic. Proto presence has the most demanding
technological requirements, and is the last of the three layers to be
addressed through media. It functions at the level of proprioception,
spatial and internal monitoring, which may reflect the primal role of these
processes in the evolution of consciousness (e.g. Sheets-Johnstone, 1998).
As yet, our ability to simulate the demands of this layer is far from
Proto presence is based on proprioception and other ways of
knowing bodily orientation in the world. In a virtual world this is
sometimes known as "spatial presence" and requires the tracking
of body parts and appropriate updating of displays. Core presence is based
largely on vividness of perceptible displays. This is equivalent to "sensory
presence" (e.g. in non-immersive VR) and requires good quality,
preferably stereographic, graphics and other displays. As already stated,
core consciousness is the pivot for judgements that something from the
world outside is impacting on the self, on the life of the organism. As
with the extended presence layer, if proto consciousness is integrated with
core consciousness, proto presence will be involved and this layer will
strengthen the overall sense of presence. The extent to which these two levels
are integrated produces what is usually called degree of immersion.
Extended presence requires intellectually and/or emotionally significant
content. Integrating the three layers amounts to fooling the system into a
conviction that something is happening to the self in the here and now.
The different layers of presence may be less than perfectly
integrated in several ways, including the following:
If you experience a VR without a
tracking system you can have high level of core presence (vividness), a
high level of extended presence (engagement) but no proto presence (spatial
If you read a good book while
sitting in an comfortable, safe place, extended consciousness will be
engaged by media (engagement) but the other layers will not be involved.
If you are in an immersive VR, but
are pre-occupied with personal worries, proto (spatial) and core presence
(vividness) will be invoked, but not extended presence.
The same situation, with
particularly uninteresting content of the VR but no dominating personal
worries (low engagement) may tend to produce frequent "breaks in
presence" (a change or spreading of position on the locus dimension).
We see changes in the locus
of presence, such as Slater's (Slater, 2002)
"breaks in presence", as illustrating how core consciousness
attempts to integrate the three levels. Content entering core consciousness
will remain there for as long as it can be integrated with the content of
the other layers. If competing contents appear at either of the other two
layers, a change in presence locus
is possible. The probability and duration of such changes depend on extended
consciousness; attention is likely to be captured by whatever is most
relevant to the goals of the extended self, whether this is a stimulus from
the real world or a mental event such as a sudden thought. Even the
occurrence of a new vivid stimulus, such as a loud sound (attracting core
presence), or a break in bodily continuity such as a cable obstructing
movement in a VR (attracting proto presence) will only have temporary
effects. Once extended consciousness has judged the event as no longer relevant,
the self will revert to the previous content of core consciousness (Spagnolli & Gamberini, 2002).
Recently, Slater (2003) has claimed that presence is determined
only by form, but our three-layer model of presence suggests that this is
an oversimplification. We suggest that proto presence is determined only by
form, core presence by both form and content, and extended presence only by
content. The integration of presence can occur in either the real or a
virtual world. In the case of a virtual world, we need to provide both
appropriate form and meaningful content. Presence in the real world depends
only on content, on what we experience as happening to us in the here and
now, since the form is provided and is always appropriate.
To maximize experienced presence in virtual environments we must
design in a way that allows integration of the three layers. As we have
seen, this is technically demanding at the lower levels. We need to provide
as much immersion as possible, integrating proto (spatial) and core
(sensory) presence. To integrate extended presence, the events and entities
experienced in the virtual environment must have significance for the
participant. One promising approach is to design a role for the participant
as a performer in a drama (Nath, 2001). It appears that if the performer
becomes emotionally or intellectually engaged by the events in an
appropriately immersive environment, high levels of presence can be
achieved (Waterworth et al., 2002). In this situation, the organism
responds as if what happens in a mediated environment is real, in the
fullest sense. Because of this, an immersive VR with appropriately engaging
content may be a uniquely effective means of addressing personal
dispositions of real significance for the individual concerned.
The purpose of presence is to provide a basis for the organism
to separate events that occur only within the self from external events
that may act on the self. Presence is experienced as a unitary feeling, a
feeling of being in a world that exists outside of the self. We have
suggested that contributions to the intensity of this feeling can come from
three layers of the self, and we refer to these as proto presence, core
presence and extended presence. The more the three layers are integrated
(focused on the same events) the stronger the intensity of the presence
The difference in presence experienced
through different media can be explained by the fact that many media
influence only a limited number of layers. In a compelling book reading
only extended consciousness is involved, and with a movie experience we can
modify both core presence and extended presence but not proto presence.
Only in immersive virtual reality are all the three layers of consciousness
modified by the media experience. We suggest that this gives immersive VR a
privileged status as a medium for meaningful experiences.
Appropriate form is needed for high
presence, but reality judgement is not only a matter of form. We are more
likely to attend to and assess information that has significance for us. At
the same time, our model allows presence to be differentiated from
emotional or intellectual engagement and, because of that, from
consciousness in general.
Baars, B. J. (1988).
A cognitive theory of consciousness.
New York: Cambridge University Press.
Damasio, A. (1999). The
Feeling of What Happens: Body, Emotion and the Making of Consciousness.
San Diego, CA: Harcourt Brace and Co, Inc.
Dennett, D. C. (1978). Brainstorms - Philosophical Essays on Mind and Psychology.
Cambridge, MA: MIT Press.
Dolan, R. J. (1999). Feeling the neurobiological self. Nature, 401, 847-848.
Farber, I. (2001). The world within the skull. Nature, 413, 776-777.
Gregory, R. L. (1998a). Brainy mind. British Medical Journal, 317,
Gregory, R. L. (1998b). Eye and Brain: The psychology of seeing (Vol. Oxford): Oxford
IJsselsteijn, W. A., & Riva, G. (2003). Being There:
The experience of presence in mediated environments. In G. Riva, F. Davide
& W. A. IJsselsteijn (Eds.), Being
There: Concepts, effects and measurements of user presence in synthetic
environments (pp. 3-16). Amsterdam: IOS Press. http://www.emergingcommunication.com/volume5.html.
Janoff-Bulman, R., & Frantz, C. M. (1997). The
impact of trauma on meaning: From meaningless world to meaningful life. In
M. Power & C. R. Brewin (Eds.), The
transformation of meaning in psychological therapies (pp. 91-106). New
Llinás, R. R. (2001). I of the vortex: From Neurons to Self. Cambridge, MA: MIT
Llinás, R. R., & Pare, D. (1991). Of dreaming and
wakefulness. Neuroscience, 44,
Metzinger, T. (1999). The hint half guessed. Scientific American, 11, 184-189.
Nath, S, (2001). Emotion Based Narratives: A New
Approach to Creating Story Experiences in Immersive Virtual Environments.
MA Thesis, Central Saint Martin's College of Art and Design, London, UK.
Sheets-Johnstone, M. (1998). Consciousness: A Natural
History. Journal of Consciousness
Studies, 5 (3) 260-294.
Slater, M. (2002). Presence and the sixth sense. Presence: Teleoperators, and Virtual
Environments, 11(4), 435–439.
Slater, M. (2003). A Note on Presence Terminology. Presence-Connect, 3, (3), January.
Slater, M., & Steed, A. (2000). A Virtual Presence
counter. Presence: Teleoperators, and
Virtual Environments, 9(5), 413-434.
Spagnolli, A., & Gamberini, L. (2002, 9-11 October).
Immersion/Emersion: Presence in
hybrid environments. Paper presented at the Presence 2002: Fifth Annual
International Workshop, Porto, Portugal.
Waterworth, J. A., & Waterworth, E. L. (2001).
Focus, Locus, and Sensus: The three dimensions of virtual experience. Cyberpsychology and Behavior, 4(2),
Waterworth, J. A., & Waterworth, E. L. (2003). The
meaning of presence. Presence-Connect,
3 (3), February.
Waterworth, J. A., Waterworth, E. L. and Westling, J.
(2002, 9-11 October). Presence as Performance: the mystique of digital
participation. Paper presented at the Presence 2002: Fifth Annual
International Workshop, Porto, Portugal.