Everyone keeps saying Eurus’ mind control powers were supernatural. They weren’t. She used two techniques, Mirroring (here’s a second link too) and the Zeigarnik effect.
In the interview with the Governor, probably with Dr. Taylor as well, she used the Zeigarnik effect by maintaining direct eye contact and using a physical tic to punctuate or interrupt what she’s saying, even when she seems to be speaking in nonsense poetry. This is a technique for tricking the subconscious that specific actions, words, or ideas are unfinished and therefore important and should be dwelt on. It creates “ear worms”.
A musical example of this this is the song Gangnam style. I’m not a musician, so have patience with my attempt to explain, essentially the meter of the song is 4/4, the musical notes tend to bunch in beats of three. This gives your brain the constant sense the song is unfinished and it sticks. You can also see it in songs like Toxic, Uptown Funk, The Power of Love, and many others where there is a sudden burst of music or sound different than the rest of the song as a sort of repetitive punctuation. It’s also why you’ll get a specific sound or single line stuck in your head over and over.
Mirroring is a subconscious tendency to speak, behave, and dress like those in your ‘family group.’ It’s a way to identify those you interact with the most and to identify those who aren’t part of the group. There are lots of reasons why I won’t get into because I burnt myself out a bit with the whole musical thing. Also, for the last half hour I’ve been looking up the specific word for when a geographical community deliberately changes the pronunciation of their town in order to identify outsiders and Google is just getting increasingly confused about what I want. Poor thing.
If you know about mirroring you can trick someone else subconsciously into listening to you and being open to you on a subconscious level. Euros does it when she mirrors Moriarty’s head movements and his sensual body language until the mirror image of her face interposes over his. She also does this with Sherlock when its shown he’s moving forward based on her body language as well as lifting his hand in time with hers.
This episode had a lot of room for improvement, but it was frustrating me that everyone seems to be saying its magic. So these are the techniques she used.