A method implemented in a computer system for controlling the delivery of data and audio/video content. The method delivers primary content to the subscriber device for viewing by a subscriber. The method also delivers secondary content to the companion device for viewing by the subscriber in parallel with the subscriber viewing the primary content, where the secondary content relates to the primary content. The method extracts attention estimation features from the primary content, and monitors the companion device to determine an interaction measurement for the subscriber viewing the secondary content on the companion device. The method calculates an attention measurement for the subscriber viewing the primary content based on the attention estimation features, and the interaction measurement, and controls the delivery of the secondary content to the companion device based on the attention measurement.