Anybody seen the movie The Gift, I think it was called, about a woman who knows her smalltown people really, really well, so she can do the Psychic thing just by intuition, but she dresses it up for money. Along comes a crime and the cops come to her for help finding the body and she has to say No, I've been faking all these years...
...but then it turns out she WAS psychic! And she starts getting flashes of where the body is, and all kinds of shenanigans ensue! Great movie, and that is how I think it works, when it appears to work.

I had a really good friend in college who often shared a mind with me, we would have the same dreams though we weren't sleeping together, or suddenly simultaneously remember something and whirl around as we were walking away from each other, and so on. Nothing supernatural, we just knew each other really, really well.

On the other hand my twins shared a mind when they were small... One baby cried and fisted his stomach, the other farted, the first stopped crying and writhing. Whose stomach ache was it? Also I could set them as schoolchildren to rock-paper-scissors and they would do the same shape, over and over again, for over half an hour, reliably. It was a great way to have some time of my own, find something they cared about who did it, and get them to pick one that way. They have outgrown it. But it WAS there, the communal/hive mind. Especially since one had motor deficits and the other was motor-gifted, they would do stuff together that took the brains of one and the brawn of the other, when they were preverbal. We called them collectively The Beast. They once took their playpen apart, moved it to another room, and put it back together, with them in it, before they were 1. They could not have colluded or collaborated, but they worked as a team.