For years, we have been trained to view web postings from our friends in a certain order. Refresh the top of your various “feeds” — the running column of content on some versions of Facebook, Twitter and Instagram — and you will see the latest news at the top. The further back you scroll, the older the material gets.
As our online networks of friends have grown larger and the social media companies have matured, the feeds have evolved. Facebook changed its news feed in 2009 by switching to an algorithm largely based on the popularity of posts, among other signals.
