Abstract
The general idea about the human-robot conversations is that the utterances of a robot should be easy to understand. It has been considered robots should provide the complete information, without the necessity of a human asking further questions. On the other hand, considering the human-human conversation, in particular, between a child and a caregiver; even though the child has a limited speaking ability to tell a story entirely, child and caregiver can build deep bonds through the aggressive support of the caregivers. This study aims to analyze the human behaviors when a robot speaks to a human with insufficient words. We built a syntactic method to create a deficiency in the elements of the robot’s utterances. We analyzed the human replies in such a human-robot conversation. The results showed that when the robot used “Kotobatarazu Utterance, ” the human partners increased asking questions to the robot, talked more about the details of the topic and they decreased slight responses. These results indicate that a human can join more actively to the conversation when the robot provides incompleteness in its conversation. Furthermore, the recorded interaction between a human and the “Kotobatarazu” robot was evaluated as cooperative.