Funnily enough I discovered this myself, doing a silly card trick with two friends. My first friend and I set up a "mind-reading" situation where he would ask the colour of the next card and I would guess. The clue was he'd say "right" or "ok" depending on whether it was black or red. We appeared to start doing it just mucking around, when we had in fact carefully rehearsed. We made sure we included a few mistakes to add credibility. We were curious to see how long it would take before our other friends rumbled us.
One other friend was amazed, so we tested her. And she found she could do it too. She got more and more excited as she got card after card right - apparently using her own "psychic powers". She was subliminally reading the same clues, of course. Her disappointment on discovering how she was really doing it was, of course, huge. I felt quite guilty.