A data processing apparatus receives data indicating a movement of a client device by a first user. The apparatus determines that the movement of the client device is a delimiter motion for switching between a first mode, in which the client device is configured to (i) provide a first interface for a first user speaking in a first language and (ii) perform speech recognition of the first language, and a second mode, in which the client device is configured to (i) provide a second interface for a second user speaking in a second language and (ii) perform speech recognition of the second language, the second interface being different from the first interface. Based on determining that the movement is a delimiter motion, the apparatus switches between the first mode and the second mode without the second user physically interacting with the client device.