# Considerations for Developing Robot-Assisted Crisis De-Escalation Practices
## 4 Integrating the De-Escalation Process into Human-Robot Interactions
### Actions to Support De-Escalation
#### 4.3.2 Non-Verbal Communication Principles
When the topic of conversation is embarrassing, however, robots that avoid eye contact are perceived more favourably [39]. When the goal of interaction was for robots to persuade their conversational partners, a natural gaze behaviour was most effective [40]. Moreover, when persuasive gestures were performed in conjunction with eye gaze, robots' persuasiveness was improved; when performed in the absence of eye gaze, persuasive gestures impeded robots' persuasiveness [41]. Finally, [PERSON] and [PERSON] [32] note that robots' gaze behaviour can be used to regulate the pace of conversations, convey mental states, and express personality and emotion. Exploring the ideal type of gaze behaviour within decascalation interactions and its impact on humans' perception and response of robots in that context will be an important area for future research. Robot movement (e.g., speed of approach) and proxemic behaviour is another active field of research e.g., [24, 42, 43, 44, 45]. Interpersonal distancing theories [46, 47] propose three functions of interpersonal distancing: (1) protection (perceived threat due to spatial invasion evokes a fight/flight with greater distance, facilitating easier escape); (2) regulation of arousal (interpersonal distance can be used to control the amount of incoming information and prevent overstimulation); and (3) communication (information about the nature of the relationship between individuals can be communicated through interpersonal distancing, such as through physical closeness). Agitated individuals are likely to be in a state of fight/flight and hyperarousal, thus their needs regarding personal space likely differ from participants typically included in studies of robot movement and proxemics. For de-escalation led by human crisis responders, slow and predictable movements are recommended. One study indicated that humans prefer robots that move more slowly than humans: approximately 1 m per second just under the average human walking speed [48]. The preference for robots to move slightly more slowly than humans under ordinary circumstances could mean that movements may need to be even slower in de-escalation situations, though this needs to be tested empirically. [PERSON] and colleagues [43] found that humans rated robots as more trustworthy when they maintained greater personal space and had a slower speed of approach; however, the authors did not specify the degrees of personal space or speeds that were used in the experiment. Ideally, the movements and proxemic behaviour of crisis responders convey a non-threatening and calm presence to agitated individuals. Robots' movement and proxemic behaviours should be designed with similar goals in mind. The idea of designing robots to move in the same manner as humans is known as social navigation and is an open area of research in robotics (see [PERSON] and [PERSON] [49] as an example). Work to date in social navigation leaves open the question as to whether humans would prefer robots to move in ways similar to or different than humans. In human-human interactions, congruence between actions and words conveys genuineness and supports a sense of trust, safety, security, and greater predictability within relationships. Above, we described a study in which greater trust was reported when the robot communicated in text rather than voice format, with this effect possibly explained by a violation of the expectation for the robot to have a more expressive and human-like voice [28]. The robot in this case could be considered \"incongruent\", in that its voice was not consistent with what participants expected based on its other qualities. Other studies within the field of human-robot interaction have noted effects related to a possible violation of expectations or \"incongruence\". [PERSON] et al.