what Rank Brain is seing is people going from social media to your website
Google does not "see" traffic from Facebook to your site, even if you're using Google Analytics. Google Analytics data is not used for ranking purposes, it is only used in the aggregate.
Rank Brain will show up your website in the results page the more your visitors interact with that same page, regardless of how.
That's not how CTR log data is used. Google does not evaluate every single user query user experience and adjust rankings in real-time.
Every kind of search query exhibits different click through patterns. Many queries have multiple user intent. For Example Query A there may be three user intents. This means the top ten of the SERPs must be divided between three user intents. These intents are ordered according to the popularity of the intent, i.e. what most of the users want to see. This is the part that screws with people's heads because they see a site at the top that the site publisher feels doesn't answer the question while there's is at position 6. The difference is that most people prefer the user intent of position 1 over that in position 6.
User interaction data within click logs is used to study and understand user intent.
Here is the part that may be new to you: Search engines can predict what user interaction may be based on that past data it studied, it can re-rank a site from position 15 and place it in position 5 because it can predict a better user experience.
However, Google takes into consideration your previous searches and can re-rank the SERPs so that it matches your user intent.
Site interaction/UX is not a ranking factor. I wrote a
4,000 word article about UX on SearchEngineJournal [searchenginejournal.com], you may wish to review that because it has links to authoritative sources of information on the topic of user interactions and how that affects rankings.