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Social rewards as praise from others enhance offline improvements in human motor skills. Does praise from artificial beings, e.g., computer-graphics-based agents (displayed agents) and robots (collocated agents), also enhance offline improvements in motor skills as effectively as praise from humans? This paper answers this question via two subsequent days’ experiment. We investigated the effect of the number of agents and their sense of presence toward offline improvement in motor skills because they are essential factors to change social effects and people’s behaviors in human-agent and human-robot interaction. Our 96 participants performed a finger-tapping task. Our results showed that those who received praise from two agents showed significantly better offline motor skill improvement than people who were praised by just one agent and those who received no praise. However, we identified no significant effects related to the sense of presence.

One of the most common cues in human relations is the reaction when someone approaches for a touch interaction. While the "before touch" distance has been investigated in daily life scenarios, it has not been studied for virtual environments. The measurements of a pre-touch distance in virtual reality can be applied to study social interactions especially for haptic interactions in virtual spaces where virtual agents interact autonomously with human participants. In the first stage of this study, we collected data to define a pre-touch distance when a virtual agent tries to touch the participant's face. On the basis of these results, we then classified participants into two groups based on preferred pre-touch distance: a "Near" group and a "Far" group. Next, we experimentally investigated the relationship between the participant's perception of an avatar's reaction to touch interaction and their preferred pre-touch distance. The results indicated that the participants felt friendliness to the agent who reacts with shorter pre-touch distance. We also found that the participant's pre-touch distance defined their preferences regarding the agent's behavior: those with a shorter pre-touch distance preferred agents with a closer interaction distance, and those with a longer pre-touch distance preferred agents with a longer interaction distance.

This paper investigates the effects of group interaction in a storytelling situation for children using two robots: a reader robot and a listener robot as a side-participant. We developed a storytelling system that consists of a reader robot, a listener robot, a display, a gaze model, a depth sensor, and a human operator who responds and provides easily understandable answers to the children’s questions. We experimentally investigated the effects of using a listener robot and either one or two children during a storytelling situation on the children’s preferences and their speech activities. Our experimental results showed that the children preferred storytelling with the listener robot. Although two children obviously produced more speech than one child, the listener robot discouraged the children’s speech regardless of whether one or two were listening.