Robots That Learn Language: Developmental Approach to Human-Machine Conversations

摘要

This paper describes a machine learning method that enables robots to learn the capability of linguistic communication from scratch through verbal and nonverbal interaction with users. The method focuses on two major problems that should be pursued to realize natural human-machine conversation: a scalable grounded symbol system and belief sharing. The learning is performed in the process of joint perception and joint action with a user. The method enables the robot to learn beliefs for communication by combining speech, visual, and behavioral reinforcement information in a probabilistic framework. The beliefs learned include speech units like phonemes or syllables, a lexicon, grammar, and pragmatic knowledge, and they are integrated in a system represented by a dynamical graphical model. The method also enables the user and the robot to infer the state of each other's beliefs related to communication. To facilitate such inference, the belief system held by the robot possesses a structure that represents the assumption of shared beliefs and allows for fast and robust adaptation of it through communication with the user. This adaptive behavior of the belief systems is modeled by the structural coupling of the belief systems held by the robot and the user, and it is performed through incremental online optimization in the process of interaction. Experimental results reveal that through a practical, small number of learning episodes with a user, the robot was eventually able to understand even fragmental and ambiguous utterances, act upon them, and generate utterances appropriate for the given situation. This work discusses the importance of properly handling the risk of being misunderstood in order to facilitate mutual understanding and to keep the coupling effective.