So, if a machine can’t run the system on its own, what will RankBrain really do? In short, it will look for patterns that humans have programmed it to look for and make pre-determined changes and adjustments based on the pattern recognition.
In truth, this isn’t true machine intelligence, it’s still a computer – albeit an incredibly powerful one – running a set of predetermined protocols and taking predetermined actions. Now, there may be some level of learning going on in the system, which theoretically would allow RankBrain to evolve its processes gradually over time. But you can rest assured that a human will still be spot-checking that evolution and making sure everything is progressing as it should.
Third Most Important Signal
Google has said that they consider the signals coming from RankBrain to be the third most important signal they base their rankings on. For a full list, you can read this great article on Search Engine Land by Danny Sullivan.