# Telepresence Social Robotics towards Co-Presence: A Review
## 2 Co-Presence Taxonomy
### Immersive Qualities  
#### 2.1.1 Modality  
The first studies on social presence analyzed the effect of the modality on the levels of presence achieved, given that the immersion degree varies. These studies on general modality identified technological features with an impact on the social presence (e.g., visual representation, interactivity, depth cues, audio quality, and display). However, medium communication comprises multiple features, and it is a challenge to discriminate the contribution of each affordance. In [42], the _media richness theory_ refers to varying the technological qualities of the medium affording distinct levels of social presence. General modality was also identified in [43] as a predictor of telepresence while analyzing the influence of immersion. Initial studies analyzed the influence of modality on social presence by comparing (1) Face-to-face (Ftf) real interactions with computer-mediated communication (CMC), (2) text-based CMC with medium's supporting visual and audio modalities, and (3) immersive virtual environments with non-immersive virtual environments. Face-to-face (Ftf) interaction is considered the ground truth for social presence [44], and several works compare face-to-face (Ftf) interaction and CMC, evaluating the capability of these mediated communications to elicit social presence. In general, these studies reveal that the sense of social presence is higher in an Ftf interaction when compared with CMC conversation. [PERSON] et al. [45] designed a task in which participants had to discuss a news article for 20 min, either with Ftf interaction or through computer-mediated communication (CMC) (chat). Communication apprehension was one of the psychological factors to be assessed (i.e., \"the level of anxiety or fear associated with either real or anticipated communication with another person or persons\"). They found that the CMC participants experienced a lower level of social presence. Researchers assessing the sociality of a partner and the level of co-location again found higher social presence levels for Ftf interaction. In studies involving decision-making scenarios [44] and in online learning achievement [46], the results privileged Ftf interaction. One study [47] involving a series of online seminars for 2 months (the same teacher teaching the same contents online and via in-person, Ftf interaction) reported no differences in the levels of social presence between both forms of interactions. One justification might be related to the fact that students had enough time to adapt their communication skills to an online learning platform, the evolution of e-learning technologies, and the fact that the students felt more comfortable not moving to a classroom for 2 months. However, this study did not address the characterization of the subjects' ages in their concluding remarks, which could reveal a tendency. Video and audio modalities guarantee higher degrees of social presence when compared with text-based CMC. However, this difference is not so clear when comparing video-audio modality against audio-only modality. Studies have shown that the introduction of video modality increases the social presence feeling if participants are required to perform visual tasks [48; 49]. In studies that compared video-audio vs. audio modalities when involving tasks that do not require visual feedback, such as interview tasks or decision-making tasks, the researchers did not report a significant difference in the social presence [50]. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline  & Immersive qualities & Modality, visual representation, interactivity, haptic feedback, audio quality, depth cues, video and display. \\ Co-presence factors & Contextual and social properties & Personality / traits of virtual human, agency, physical proximity, task type, social cues, identity cues. \\ Individual traits & Demographic variables, psychological traits. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Categorization of predictors.