A method of initiating and controlling computer user behavioural data (e.g., emotional state information) collection and processing within the structure of a video ad response provides an analysis of video ad effectiveness as a result of interaction with the computer user. A behavioural data collection and processing module is caused to run by the execution of a Video Ad Standard Template (VAST) compliant video ad response in a video player. The data collection and processing module may be obtained by calling a resource identifier contained in the video ad response, or by providing an executable application within the served video ad response itself. In more particular methods according to the invention, processing of collected data is managed so as to improve the efficiency of media playback at the client computer and communications with remote servers.