Presence (telepresence)

Presence is a theoretical concept describing the extent to which media represent the world (in both physical and social environments). Presence is further described by Matthew Lombard and Theresa Ditton as “an illusion that a mediated experience is not mediated." Today, it often considers the effect that people experience when they interact with a computer-mediated or computer-generated environment. The conceptualization of presence borrows from multiple fields including communication, computer science, psychology, science, engineering, philosophy, and the arts. The concept of presence accounts for a variety of computer applications and Web-based entertainment today that are developed on the fundamentals of the phenomenon, in order to give people the sense of, as Sheridan called it, “being there." 
Evolution of 'presence' as a concept.
The specialist use of the word “presence” derives from the term “telepresence”, coined by Massachusetts Institute of Technology professor Marvin Minsky in 1980. Minsky's research explained telepresence as the manipulation of objects in the real world through remote access technology. For example, a surgeon may use a computer to control robotic arms to perform minute procedures on a patient in another room. Or a NASA technician may use a computer to control a rover to collect rock samples on Mars. In either case, the operator is granted access to real, though remote, places via televisual tools.
As technologies progressed, the need for an expanded term arose. Sheridan extrapolated Minsky’s original definition. Using the shorter “presence,” Sheridan explained that the term refers to the effect felt when controlling real world objects remotely as well as the effect people feel when they interact with and immerse themselves in virtual reality or virtual environments.
Lombard and Ditton went a step further and enumerated six conceptualizations of presence:
Lombard's work discusses the extent to which 'presence' is felt, and how strong the perception of presence is regarded without the media involved. The article reviews the contextual characteristics that contribute to an individual's feeling presence. The most important variables that are important in the determinants of presence are those that involve sensory richness or vividness - and the number and consistency of sensory outputs. Researchers believe that the greater the number of human senses for which a medium provides stimulation, the greater the capability of the medium to produce a sense of presence. Additional important aspects of a medium are visual display characteristics (image quality, image size, viewing distance, motion and color, dimensionality, camera techniques) as well as aural presentation characteristics, stimuli for other senses (interactivity, obtrusiveness of medium, live versus recorded or constructed experience, number of people), content variables (social realism, use of media conventions, nature of task or activity), and media user variables (willingness to suspend disbelief, knowledge of and prior experience with the medium). Lombard also discusses the effects of presence, including both physiological and psychological consequences of "the perceptual illusion of nonmediation." 
Physiological effects of presence may include arousal, or vection and simulation sickness, while psychological effects may include enjoyment, involvement, task performance, skills training, desensitization, persuasion, memory and social judgement, or parasocial interaction and relationships.
Presence has been delineated into subtypes, such as physical-, social-, and self-presence. Lombard's working definition was "a psychological state in which virtual objects are experienced as actual objects in either sensory or nonsensory ways." Later extensions expanded the definition of "virtual objects" to specify that they may be either para-authentic or artificial. Further development of the concept of "psychological state" has led to study of the mental mechanism that permits humans to feel presence when using media or simulation technologies. One approach is to conceptualize presence as a cognitive feeling, that is, to take spatial presence as feedback from unconscious cognitive processes that inform conscious thought.
Case studies.
Several studies provide insight into the concept of media influencing behavior.