# Social Distance in Interactions between Children with Autism and Robots
## 1 Introduction
### HRI in Autism Therapy  
ASD is a developmental disorder characterized by speech delay, difficulty with interpersonal interactions, and a strong fixated interest in specific subjects [19]. According to a 2012 report, among seven major countries, Japan ranks second in the prevalence of autistic individuals after the United States [20]. ASD includes lifelong disorders that affect communication skills and the ability to understand and respond to social cues. ASD may also be associated with intellectual disabilities or other disorders such as hyperesthesia. Against this background, ASD was redefined as a continuum of various autism disorders, thus eliminating the boundaries with the typical [21]. ASD is also considered a congenital brain disorder. Other features of the disorder include non-responsiveness to calls, hypersensitivity and dullness, poor concentration, and poor attention and memory. Symptoms such as difficulty in controlling emotions, immediate panic, and dislike of changes in the environment are also observed [22].  
Robot therapy is a form of psychotherapy aimed at improving symptoms of autism and dementia through mediation by robots. Several experiments in which this method was applied confirmed the positive effects of using robots in therapy with children. These experiments have also led to greater knowledge that better supports people with ASD [23]. Among individuals with autism, reading complex human facial expressions is difficult. Since robots have simpler structures than humans, children with autism find it easier to interpret the social and communication cues, and thus actively communicate with the robot [10]. Therefore, by communicating with a robot, children with autism can improve their communication skills [12; 24]. For example, [PERSON] et al. examined the effects of verbal communication between autistic children and humans, and then robots [10]. Their results revealed that autistic children could follow the words of the robots rather than that of humans. [PERSON] et al. similarly examined the effectiveness of robot therapy from three modalities (audio, visual, and autistic physiology) [25]. [PERSON] et al. gave blocks to a child with autism while the robot gave commands asking the child to perform tasks, such as stacking and breaking [26]. The analysis method examined the cooperative state in which the participant was cooperating and performing the intended actions and the conflict state in which the participant was taking a non-intended action. It was suggested that the participant could understand the intention and independence of the robot's behaviors and communicate naturally by gazing.  
The following is a brief description of the most well-known robots used in robot therapy for autistic children. KASPAR is a child-sized robot developed by the Adaptive Systems Research Group at the University of Hertfordshire [27]. This technology is capable of making human facial expressions and gestures. Therefore, a game is played between autistic children, and KASPAR is used for emotional training. Keepon was developed by the CareBots Project and has a yellow dango-shaped body (height 120 mm, diameter 80 mm) [28]. The upper dango comprises the head, with a wide-angle video camera marking the left and right eye and a microphone attached to the nose. The dango on the side corresponds to the belly. Keepon has four degrees of freedom, and it expresses its state of mind through gestures. QTrobot is a robot designed by artificial intelligence with a liquid crystal display face and a robot arm made by LuxAI [29]. It enhances the emotion recognition abilities of autistic children by imitating the emotions of children with expressive faces and moving arms. The robot's behavior is partly fixed and it never denies the child. By using the attached tablet terminal, the QTrobot interacts with the child, arousing the child's interest and reducing confusion.