> Twitter invents the “pull-to-refresh” UI gesture that leverages variable rewards to trigger addictive behavior as a way to increase user engagement with the timeline; Facebook invents the “red dot” notifications that keep people checking their phone for the next new thing.

two minor corrections:

1) pull-to-refresh was not invented by Twitter, but by Tweetie, a third-party Twitter client.

2) The "red dot" for notifications was not invented by Facebook, but most likely first appeared on Apple’s mail.app about 20 years ago in the first version of Mac OS X.