Google is reportedly using Opinion Rewards to gather feedback on YouTube's recommended videos functionality. While the surveys can ask questions from a varied pool of categories, Google can also use the app to get some useful feedback on their own products and services, and that appears to be what they're doing with YouTube in an attempt to improve the recommended videos that people see in their lists when they open up the app or visit the website. As Google Opinion Rewards surveys aren't popping up all of the time there is a very good chance that many users won't see this survey show up immediately, but this is one to look out for as it seems to be appearing for some users.
Having said that, there is no way to know when this survey will show up for you as surveys tend to pop up randomly with no rhyme or reason to how many one user gets compared to another. You do need to have YouTube's watch history feature enabled though if you want this particular survey to show. During the survey, it starts out by asking the user about a video that they may have watched through the service, asking if they had viewed it on YouTube earlier. The survey then proceeds with asking whether or not the next video shown would be a good recommendation based on the first video. There appears to be four questions, the last three of which seem to be asking if the video displayed on screen would be a good fit for a recommendation.
This wouldn't be the first time that Google had been asking survey questions about one of their products, as Opinion Rewards was asking various users about Project Ara back in March. Also in March but earlier than the survey about Project Ara, the Google Opinion Rewards app was asking people about their favorite tasty treats, and the survey was complete with a collective of options that all started with the letter N. This was of course before Google had seemingly settled on the name for Android 7.0 (now Nougat) which some had speculated was Google's way of trying to get assistance on deciding what the name should be. If you'd like the chance to see this survey pop up, make sure YouTube's watch history is enabled and then just wait patiently, although there is no guarantee that the you will receive this particular survey.