Audio-Visual Stimuli Change not Only Robot’s Hug Impressions but Also Its Stress-Buffering Effects

A HUG taxonomy of humans with potential in human-robot hugs

Humans can easily perform various types of hugs in human contact and affection experience. With the prevalence of robots in social applications, they would be expected to possess the capability of hugs as humans do. However, it is still not an easy task for robots, considering the complex force and spatial constraints of robot hugs. In this work, we propose the HUG taxonomy, which distinguishes between different hugging patterns based on human demonstrations and prior knowledge. In this taxonomy, hugs are arranged according to (1) hugging tightness, (2) hugging style, and (3) bilateral coordination, resulting in 16 different hug types. We then further study the hug type preference of humans in different scenarios and roles. Furthermore, we propose a rule-based classification system to validate the potential of this taxonomy in human-robot hugs based on a humanoid robot with an E-skin of contact sensation. The HUG taxonomy could provide human hugging behavior information in advance, facilitating the action control of humanoid robots. We believe the results of our work can benefit future studies on human-robot hugging interactions.

Embodied, visible, and courteous: exploring robotic social touch with virtual idols

In recent years, virtual idols have garnered considerable attention because they can perform activities similar to real idols. However, as they are fictitious idols with nonphysical presence, they cannot perform physical interactions such as handshake. Combining a robotic hand with a display showing virtual idols is the one of the methods to solve this problem. Nonetheless a physical handshake is possible, the form of handshake that can effectively induce the desirable behavior is unclear. In this study, we adopted a robotic hand as an interface and aimed to imitate the behavior of real idols. To test the effects of this behavior, we conducted step-wise experiments. The series of experiments revealed that the handshake by the robotic hand increased the feeling of intimacy toward the virtual idol, and it became more enjoyable to respond to a request from the virtual idol. In addition, viewing the virtual idols during the handshake increased the feeling of intimacy with the virtual idol. Moreover, the method of the hand-shake peculiar to idols, which tried to keep holding the user's hand after the conversation, increased the feeling of intimacy to the virtual idol.

Human Factors Considerations for Quantifiable Human States in Physical Human-Robot Interaction: A Literature Review

As the global population rapidly ages with longer life expectancy and declining birth rates, the need for healthcare services and caregivers for older adults is increasing. Current research envisions addressing this shortage by introducing domestic service robots to assist with daily activities. The successful integration of robots as domestic service providers in our lives requires them to possess efficient manipulation capabilities, provide effective physical assistance, and have adaptive control frameworks that enable them to develop social understanding during human-robot interaction. In this context, human factors, especially quantifiable ones, represent a necessary component. The objective of this paper is to conduct an unbiased review encompassing the studies on human factors studied in research involving physical interactions and strong manipulation capabilities. We identified the prevalent human factors in physical human-robot interaction (pHRI), noted the factors typically addressed together, and determined the frequently utilized assessment approaches. Additionally, we gathered and categorized proposed quantification approaches based on the measurable data for each human factor. We also formed a map of the common contexts and applications addressed in pHRI for a comprehensive understanding and easier navigation of the field. We found out that most of the studies in direct pHRI (when there is direct physical contact) focus on social behaviors with belief being the most commonly addressed human factor type. Task collaboration is moderately investigated, while physical assistance is rarely studied. In contrast, indirect pHRI studies (when the physical contact is mediated via a third item) often involve industrial settings, with physical ergonomics being the most frequently investigated human factor. More research is needed on the human factors in direct and indirect physical assistance applications, including studies that combine physical social behaviors with physical assistance tasks. We also found that while the predominant approach in most studies involves the use of questionnaires as the main method of quantification, there is a recent trend that seeks to address the quantification approaches based on measurable data.

The Long-Term Efficacy of "Social Buffering" in Artificial Social Agents: Contextual Affective Perception Matters

In dynamic (social) environments, an affective state of "stress" can be adaptive and promote agent wellbeing, but maladaptive if not appropriately regulated. The presence of (and interactions with) affect-based social support has been hypothesised to provide mechanisms to regulate stress (the "social buffering" hypothesis), though the precise, underlying mechanisms are still unclear. However, the hormone oxytocin has been implicated in mediating these effects in at least two ways: by improving social appraisals and reducing the short-term release of stress hormones (i.e., cortisol), and adapting an agent's long-term stress tolerance. These effects likely facilitate an agent's long-term adaptive ability by grounding their physiological and behavioural adaptation in the (affective) social environment, though these effects also appear to be context-dependent. In this paper, we investigate whether two of the hypothesised hormonal mechanisms that underpin the "social buffering" phenomenon affect the long-term wellbeing of (artificial) social agents who share affective social bonds, across numerous social and physical environmental contexts. Building on previous findings, we hypothesise that "social buffering" effects can improve the long-term wellbeing of agents who share affective social bonds in dynamic environments, through regular prosocial interactions with social bond partners. We model some of the effects associated with oxytocin and cortisol that underpin these hypothesised mechanisms in our biologically-inspired, socially-adaptive agent model, and conduct our investigation in a small society of artificial agents whose goal is to survive in challenging environments. Our results find that, while stress can be adaptive and regulated through affective social support, long-term behavioural and physiological adaptation is determined by the contextual perception of affective social bonds, which is influenced by early-stage interactions between affective social bond partners as well as the degree of the physical and social challenges. We also show how these low-level effects associated with oxytocin and cortisol can be used as "biomarkers" of social support and environmental stress. For socially-situated artificial agents, we suggest that these "social buffering" mechanisms can adapt the (adaptive) stress mechanisms, but that the long-term efficacy of this adaptation is related to the temporal dynamics of social interactions and the contextual perception of the affective social and physical environments.

How Can Robots Make People Feel Intimacy Through Touch?

This study investigates the effects of the touch characteristics that change the intimacy perceived by humans in human-robot touch interaction with an android robot having a human-like feminine appearance. Past studies on human-robot touch interaction focused on understanding which types of human touches are used to express emotions to robots. However, they less focused on how a robot’s touch characteristics can affect humans’ perceived intimacy. In this study, first, we concentrated on two types of touch characteristics (type and place) and their effects on the perceived intimacy of a commonly used emotion in human-robot interaction, namely happiness. The results showed that the touch types are useful for changing the perceived intimacy, although the touched place did not exhibit any significant effects. Based on the results of our first experiment, we investigated the effects of different touch characteristics (length and part). We concluded that the touch part is useful to change the perceived intimacy, although the touch length did not exhibit any significant effects. Finally, the results suggested that a pat (type) by the fingers (part) is a better combination to express intimacy with our robot.

Effect of Robot’s Play-Biting in Non-Verbal Communication

This paper focuses on “play-biting” as a touch communication method used by robots. We investigated an appropriate play-biting behavior and its effect on interaction. The touching action has positive effects in human-robot interactions. However, as biting is a defenseless act, it may cause a negative effect as well. Therefore, we first examine biting manner and the appearance of the robot using a virtual play-biting system in Experiment 1. Next, based on the result of experiment, the play-biting system is implemented in a stuffed animal robot. We verified the impressions created by the robot and its effect on mitigating stress in Experiment 2. Consequently, the play-biting communication gave positive and lively impression, and effect of reducing the physiological index of stress, in comparison to only touching the robot.

Gaze-Height and Speech-Timing Effects on Feeling Robot-Initiated Touches

This paper reports the effects of communication cues on robot-initiated touch interactions at close distance by focusing on two factors: gaze-height for making eye contact and speech timing before and after touches. Although both factors are essential to achieve acceptable touches in human-human touch interaction, their effectiveness remains unknown in human-robot touch interaction contexts. To investigate the effects of these factors, we conducted an experiment whose results showed that being touched with before-touch timing is preferred to being touched with after-touch timing, although gaze-height did not significantly improve the feelings of robot-initiated touch.