The move is characterized by Google as a test, to assess both an ad's level of engagement as well as the type of people who might watch it. The company said the test may inform future ad models based on engagement alone and not click-throughs.
Google increasingly is leveraging its YouTube unit with new ad tactics. Last month the company launched its Promoted Videos ad model, combining Google AdWords with YouTube videos to display video ads based on keyword queries.
YouTube experiences search volume that is second only to Google itself, according to Internet tracking company comScore.