If users point backs to the search results after reading the author tagged article for a certain period of time, Google will add three more additional links to similar articles referring to the same author below the clicked link. If the user clicks on the search results with author tagged, and after reading a post on a site, he hits back button to return to the Google SERP (Search Engine Result Page), then the original result will show several extended links referring to other content by the same author. But result only triggers if user stayed on the page for some amount of time. Google will add a new “More by Author Name” indicating three more additional links to the article. Refer to Snapshot below:
If user makes use of back button very quickly or go back to the search result page fast then no extra links will appear, as Google is measuring the time that the user spares on reading that article, if Google thinks that you enjoyed reading the article or was informative then only it will show up extra links. In this case, engagement is measured in the amount of time user spends on that piece of content. This also confirms that creating content that actually engages people and gets read will be an important factor in AuthorRank, as Google obviously wants to show more results from the same author in that event.
Google did, though, confirm that this is part of the authorship feature:
If a user visits an article by an author and it seems like they’d be interested in finding more articles by this author, when they click the “Back” button to return to the results page, we’ll show more results by that author. His article is highly recommended reading.