This paper presents an intelligence model for conversational service robots. It employs modules called experts, each of which is specialized to execute certain kinds of tasks such as performing physical behaviors and engaging in dialogues. Some of the experts take charge in understanding human utterances and deciding robot utterances or actions. The model enables switching and canceling tasks based on recognized human intentions, as well as parallel execution of several tasks. This model specifies the interface that an expert must have, and any kind of expert can be employed if it conforms to the interface. This feature makes the model extensible.Key words: conversational robot, conversational agent, robot intelligence, behavior and dialogue control, multi-expert model ⋆ This paper is a considerably extended version of [1]. We thank the Association for Computational Linguistics for permission to reuse the material.