## 3 Presentation to the Participants
### Virtual Reality Systems/Devices
In [28], the Vizard Virtual Reality Toolkit is used to develop a virtual 360-degree classroom that is delivered to a participant via a head-mounted display. Due to the 360-degree virtual environment, a participant would have to turn his/her head up to 60 degrees left or right to see all avatars in the scene. Vizard is also used in [44; 58] to create virtual reality scenes. In [59], the Game Studio A6 rendering engine from Conitec, Germany was used to produce the avatars and the corresponding scenes used in their study. In this study, the participants were asked to identify the emotion of the avatar, which could be happy, sad, surprise, anger, disgust, and fear. A participant was allowed to control the virtual distance between the participant and the avatar via joystick so that he/she could position the avatar to the most comfortable distance for emotion identification. For each emotion, there are four levels of emotional intensity (ranging from vague, neutral, to clear and strong) with corresponding facial expression (at 10, 40, 70, and 100%) and body gesture (such as \"clasp hands, raise shoulder, shakes head, arms crossed, look down, step back\" [59]). Furthermore, the rendering engine also enabled lip-synch animation to increase the fidelity of the verbal interaction. Another platform used by researchers for virtual avatar-based scene production is the Unity game engine from Unity Technologies. Different from the Vizard Virtual Reality Toolkit and Game Studio A6, other modeling and animation tools are needed for dynamic facial expression design and animation. In [60], the Maya tool from autodesk was used to animate the characters taken from Mixamo ([[http://www.mixamo.com](http://www.mixamo.com)]([http://www.mixamo.com](http://www.mixamo.com))). In this study, seven universal facial expressions were used, including \"joy, surprise, contempt, sadness, fear, disgust, and angle\" (page 1644) [60]. For each emotional expression, four emotion intensity levels were animated (low, medium, high, and extreme), which correspond to four different difficulty levels in facial expression recognition where the lower intention level the more difficult to recognize. Unity is also used in [61] for virtual reality production, where both static and animated avatars are used and are capable of making ten different facial motions, including happiness, anger, disgust, fear, sadness, surprise, pain, neutral, and funny face. Unlike other studies, in [61], a game controller (referred to as gamepad in the paper) was used to control the avatars, control the cursors for answering questions, and receive vibration based tactile feedback. In addition to facial expression, the gait could also reflect the emotion of a person. Hence, some studies have focused using polygonal walking avatars to produce emotional gait stimuli. Similar to facial expressions, gait can also be morphed into different intensity levels. In [62], three levels of intensity are used, ranging from attenuated (50%), prototypical (100%), and exaggerated (150%). The emotion can be expressed via the flexion of the head and arms, as well as the torso positioning [63]. For example, the happy emotion can be expressed by tilting the head backward and leaning back the torso, and the anger emotion can be expressed by tiling the head forward and leaning forward the torso. In [64], the design of avatar has included the consideration that individuals with ASD tend to suffer from sensory overload, which refers to a phenomenon where an individual with ASD could choose to block all external stimuli when he/she is presented with too many cues concurrently. Hence, the authors of [64] chose to use a 2D cartoon-like avatar with predictable eye blink and head tilt patterns (the avatar links once every 5 s and tilts its head to the side once every 5 s as well). In some studies, virtual avatars are placed in specific scenes that is consistent with the story told by the avatars. For example, if a story is about an incident in a fast food restaurant, the scene could be McDonald's.