# Telepresence Social Robotics towards Co-Presence: A Review
## 3 From Telepresence to Co-Presence Design
### Evaluation Methods  
To assess co-presence, telepresence systems require objective and qualitative metrics. Quantitative measures may include physiological signals (such as heart rate, skin temperature, electrodermal activity (EDA), and skin conductance responses (SCRs) [229], eye scan patterns, electroencephalography (EEG), or functional magnetic resonance imaging (fMRI)) [34; 230; 231], as well as other metrics that are simpler to obtain, such as accuracy, time to perform a task, and the number of errors or communication delays. However, given the human factor and the psychological components of interaction, questionnaires remain essential tools. There are methodologies for measuring the _presence_, _social presence_ or _co-presence_, and _flow state_ of the users using technological devices [19; 232; 233; 234; 235].  
_Flow_ is a psychological state that people describe when they are fully engaged in some events to the point of forgetting time, fatigue, and everything else but the activity itself [40; 236]. Table 11 lists the available questionnaires to measure the levels of presence, co-presence, immersion, and flow.  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Type** & **Voluntary** & **Involuntary** \\ \hline Eye contact & X & - \\ Gaze following & X & - \\ Gazing at the closest face & X & - \\ Gazing at a random face & X & - \\ Gazing at the closest object & X & - \\ Gazing at a random object & X & - \\ Gazing at a moving object & X & - \\ Looking around the gazing position & X & - \\ Joint attention & X & - \\ Sleeping & X & - \\ Changing LED colors & X & - \\ Mouth movement & X & - \\ Nodding in response to human speech & X & - \\ Waving both hands at a random human & X & - \\ Waving left hand at a random human & X & - \\ Waving right hand at a random human & X & - \\ Waving left hand in response to palms & X & - \\ Waving right hand in response to palms & X & - \\ Waving both hands in response to palms & X & - \\ Reflexive blinking with eye movement & - & X \\ Spontaneous blinking & - & X \\ Avoiding objects at close range & - & X \\ Eye saccade & - & X \\ Breathing & - & X \\ \hline \hline \end{tabular}
\end{table}
Table 10: Robotic mechanisms to enhance co-presence.  
Usability, testing and accessibility-Jakob [PERSON], one of the most active proponents of usability processes, referred to the following elements that comprise a definition of usability [249, 250, 251]:  
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2. Ease of use: the use of products or tasks should be natural and easily performed by the user.
3. Simplicity of learning: tasks and product features must be intuitive and present a logical and consistent sequence to simplify learning.
4. Improved reliability: levels of satisfaction and performance are increased when the action's results correspond to the user's expectations.
5. Reduction in errors: usability can be increased if designers attribute the errors to the product or task (rather than the user), redesigning it based on the user's feedback.
6. Enhanced user satisfaction: the user's satisfaction principle must guide all of the design process, making the product or task pleasing to use or perform.  
In [252], a taxonomy of usability guidelines for the design of telepresence teleoperated robots (interaction effectiveness and efficiency, information presentation, interface visual design, robot surroundings and environment awareness, robot state awareness, and cognitive factors) is proposed. The usability testing process is an effective use of materials and time [17, 249, 253, 254] that should not be overlooked.