Semantic-Free Utterances (SFUs, sounds conveying intention without using words) are being increasingly adopted for human-robot interaction (HRI) to communicate affect. In healthcare, where older adults are overrepresented, affective robotics are becoming more common to reduce healthcare professionals' workload. Hence, understanding how older adults perceive and communicate with robots is crucial. Although previous studies have demonstrated a decline in older adults' ability to categorize emotions, it remains unclear how this impacts their comprehension of SFUs used in HRI. This paper investigates the effect of age (and other factors) on listeners' ability to categorize emotions in SFUs designed for HRI. Additionally, we explore listeners' preferences of SFUs for a healthcare robot. Listeners indicated that SFUs' similarities to natural language, the need for a distinction between human and robot, and their expectations of how a hospital robot should sound like, influenced their preferences. Furthermore, we conducted an online emotion categorization task to investigate how age, emotion category, type of SFU (with varying degrees of robot-likeness), listeners' gender, and their experience with robots relate to listeners' ability to categorize emotions. Results confirm that as age increases, there is a decline in emotion categorization performance of SFUs varying by emotion category and type of SFU.

In order to calibrate children’s trust in robots toward appropriate levels in the interaction, reliable trust measures are necessary. Current trust measures are not suitable for measuring children’s trust in a real-time manner. While speech from adult speakers has proven to contain information on their trust, this paper presents a first exploration investigating whether these results hold up in the context of a child-robot interaction. Fifty-eight conversations between children and robots were recorded (N=29), evoking high and low trust moments in the interaction. Correlation tests showed no (strong) predictors of children’s trust in their speech. Limitations and possibilities of how to advance the investigations of an automatic trust measure for child-robot interaction are discussed.

To be seamlessly integrated in human-centered environments, robots are expected to have intelligent social capabilities on top of their physical abilities. To this end, research in artifi-cial intelligence and human-robot interaction face two major challenges. Firstly, robots need to cope with uncertainty during interaction, especially when dealing with factors that are not fully observable and hard to infer (latent variables) such as the states representing the dynamic environment and human behavior (e.g., intents, goals, preferences). Secondly, robots need to communicate their behaviors to agents (humans and other robots in the environment) in a clear and understandable manner. Therefore, robots need to be context-aware: being able to perceive and understand their surroundings, and adapt their functionalities accordingly.

Unpredictability in robot behaviour can cause difficulties in interacting with robots. However, for social interactions with robots, a degree of unpredictability in robot behaviour may be desirable for facilitating engagement and increasing the attribution of mental states to the robot. To generate a better conceptual understanding of predictability, we looked at two facets of predictability, namely, the ability to predict robot actions and the association of predictability as an attribute of the robot. We carried out a video human-robot interaction study where we manipulated whether participants could either see the cause of a robot’s responsive action or could not see this, because there was no cause, or because we obstructed the visual cues. Our results indicate that when the cause of the robot’s responsive actions was not visible, participants rated the robot as more unpredictable and less competent, compared to when it was visible. The relationship between seeing the cause of the responsive actions and the attribution of competence was partially mediated by the attribution of unpredictability to the robot. We argue that the effects of unpredictability may be mitigated when the robot identifies when a person may not be aware of what the robot wants to respond to and uses additional actions to make its response predictable.

Predictability is important to autistic individuals, and robots have been suggested to meet this need as they can be programmed to be predictable, as well as elicit social interaction. The effectiveness of robot-assisted interventions designed for social skill learning presumably depends on the interplay between robot predictability, engagement in learning, and the individual differences between different autistic children. To better understand this interplay, we report on a study where 24 autistic children participated in a robot-assisted intervention. We manipulated the variance in the robot’s behaviour as a way to vary predictability, and measured the children’s behavioural engagement, visual attention, as well as their individual factors. We found that the children will continue engaging in the activity behaviourally, but may start to pay less visual attention over time to activity-relevant locations when the robot is less predictable. Instead, they increasingly start to look away from the activity. Ultimately, this could negatively influence learning, in particular for tasks with a visual component. Furthermore, severity of autistic features and expressive language ability had a significant impact on behavioural engagement. We consider our results as preliminary evidence that robot predictability is an important factor for keeping children in a state where learning can occur.

A commonly used argument for using robots in interventions for autistic children is that robots can be very predictable. Even though robot behaviour can be designed to be perceived as predictable, a degree of perceived unpredictability is unavoidable and may sometimes be desirable to some extent. To balance the robot's predictability for autistic children, we will need to gain a better understanding of what factors influence the perceived (un)predictability of the robot, how those factors can be taken into account through the design of the interaction, and how they influence the autistic child-robot interaction. In our work, we look at a specific type of predictability and define it as “the ability to quickly and accurately predict the robot's future actions”. Initial results show that seeing the cause of a robot's responsive actions influences to what extent it is perceived as being unpredictable and its competence. In future work, we will investigate the effects of the variability of the robot's behaviour on the perceived predictability of a robot for both typically developing and autistic individuals.