Google Ranking Factor – Logged-in User’s Past Behavior
Google will watch a user’s individual behavior and tailor a search result to them if it thinks appropriate.
Yes, they are watching you every move. You can view data about your Google user activity here. If you are concerned about how Google might be using your activity history, you can clear it and turn features off, but that’s no guarantee that the data isn’t being collected anyway. You just won’t benefit from it anymore.
That means if the user has visited a particular site many times from Google search, then the site will artificially gain rank, but only for the specific user. The user’s G-SERPs user profile will travel with the user if the user has several logged-in devices using Google services, and that’s transferred across devices too.
Clicks to a site from other than Google search, such as via bookmark, cannot be attributed to this model unless a tagged URL is passed to another system.
Tagged URLs have extra data in the URL to signal to Google how a user came to find a particular resource. Next time you perform a few Google searches, look carefully in the browser address bar to see how consecutive searches build a larger tag with progressively more information about your behavior when using their system.