Hi Emily, thank you! Did you read Larry Kim’s RankBrain and CTR post over at Moz, by chance? :) https://moz.com/blog/does-organic-ctr-impact-seo-rankings-new-data “RankBrain may just be the missing link between CTR and rankings.” Larry and his data have me convinced. And I’m remembering that this CTR and rankings connection was predicted in Rand Fishkin’s 2015 Pubcon keynote http://www.bruceclay.com/blog/seo-in-a-two-algorithm-world-pubcon-keynote-by-rand-fishkin/ so I could see the connective tissue lying in RankBrain, sure. I’m not an engineer, but it all follows to me.

Rankbrain’s focus is on understanding query intent, so in and of itself, has no direct impact on CTRs. It’s output can have an impact on CTR, however. If it does it’s job well, the query results should more closely match the searcher’s intent, therefore better results are at the top, garnering more clicks and impacting CTR.