In Stephen’s study, the more the brains were synced up the more the listener understood the ideas and message from the speaker. And by watching what parts of the brain were lighting up, Stephens could see that the parts of the brain that have to do with prediction and anticipation were active. The more active they were, the more successful was the communication.

https://www.blog.theteamw.com/2011/03/21/100-things-you-should-know-about-people-87-speaker-and-listener-brains-sync/