In one aspect, a method for operating a virtual agent will be described. An interaction context is obtained. An agent state is determined based on the obtained interaction context. The agent state indicates an activity of the virtual agent. The emotion of the virtual agent is updated based on the obtained interaction context, the determined agent state and/or a personality of the virtual agent. One or more behaviors are selected. Each behavior involves or indicates a change in an appearance of the virtual agent or generation of audio. Various embodiments relate to devices, servers, software and systems arranged to implement one or more of the above operations.