

I know for a fact that the algorithm retains data about your viewing preferences even after deleting watch history. After deleting mine it would still occasionally recommend something I’ve seen before and can pretty easily corral me back into whatever direction I had previously gone in. After having done this many times the videos became more random, so I think it keeps a few data points to “jump start” your viewing experience but they gradually change. If you reset your history and view as many random new videos as you can, rinse and repeat, they eventually use those those as starting points.
Mom would be sad.