Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for classifying voice inputs. The methods, systems, and apparatus include actions of providing an answer to a first voice input from a user and receiving visual or audio data corresponding to a second voice input. Further actions include classifying the second voice input as a follow on request to the first voice input or as deliberation on the answer, based on the visual data or the audio data. Additionally, the actions include determining whether to provide a response to the second voice input based on the classification of the second voice input.