The recognition of indicated objects by interacting people is an essential function for robots that act in daily environments. However, due to ambiguous references by them, accurate recognition of indicated objects have difficulties for the robots. For example, people sometimes use the words which did not contain in the robots' databases, or they did not use enough words to identify the object. Therefore, to improve recognition accuracy, we must decrease such ambiguity of indicating behaviors of people. For this purpose, we experimentally compared two kinds of interaction strategies to decrease the ambiguity: explicitly providing requests to people about how to refer to objects, or implicitly aligning with people's indicating behaviors. The experimental results showed that participants evaluated the implicit strategy to be more natural than the explicit strategy, and the recognition performances of the two strategies were not significantly different.
