1. A method comprising: determining that one or more entities in visual content, which is displayed on a display of a processing system, are selected in accordance with an explicit scoping command from a user, the explicit scoping command identifying the one or more entities in the visual content to explicitly indicate a scope of an interaction between the user and the processing system; turning on speech understanding functionality of the processing system, using at least one processor of the processing system, in response to determining that the one or more entities are selected, the speech understanding functionality enabling the processing system to understand natural language requests; and automatically monitoring audio signals received via an audio interface of the processing system for speech requests from the user to be processed using the speech understanding functionality in response to determining that the one or more entities are selected.