For customized categories, the machine learning is optimizing for ordering the articles as closely as possible to how the user rated them. There are other optio

For customized categories, the machine learning is optimizing for ordering the articles as closely as possible to how the user rated them. There are other options, like optimizing to clicks, but that can end up with more tabloidy articles than most users like. Our hope is by optimizing to explicit ratings, users will be able to find content that is more deeply interesting.