Abstract: Among other things, a succession of conversations are facilitated between a user of a device and a non-human companion portrayed on the device, to develop a relationship between the user and the non-human companion over a time period that spans the successive conversations. The relationship is developed between the user and the non-human companion to cause a change in a state of the user over the time period. Each of the successive conversations is facilitated by actions that include the following. A segment of speech of the non-human companion is presented to the user. A segment of speech of the user is detected. The user's segment of speech and the segment of speech presented to the user include portion of the conversation. At the device, information is received from an intelligent agent about a next segment of speech to be presented to the user, as determined by the intelligent agent based on intelligent processes applied to the segment of speech of the user and to the change in state to be caused.