I've always viewed the Bene Geserit as a hybrid between highly trained monks and incredibly talented diplomats. The control over one's body that could be achieved if we trained from a very young age would be incredible. I believe there's an appropriate quote that goes something like - knowing a thing can be done is half the effort of doing it. The perception and attention to nuance achieved from heightened states of mental alertness would allow for a level of prediction and anticipation in the observed that would probably frighten most people. What I think would be needed to achieve this are rules and training. If you could think of behaviour like a language with its rules, syntax and grammar you might be able to learn to understand more than the basics i.e., smile, frown, etc. We would need to understand what motivates people and how to utilize those desires to achieve our goals. Dale Carnegie wrote a book called "How to win friends and influence people" the title is a bit quaint by today's standards but the information is still incredibly useful. People haven't changed that much in the 66 years since he wrote it. God only knows how many times its been reprinted. In the Asimov universe a single human is unpredictable but the behaviour of a large population is. Psychohistory utilizes the theories of the behaviours of gas particles in much of its mathematics. But I digress
