A macro effect is a magic trick or mentalism effect in which everyone in the audience participates in the effect simultaneously. The prolific mentalist Bob Cassidy was the first mentalist to use the terms “micro effect” and “macro effect” applied to mentalism. In a micro effect, someone in the audience thinks of something and the mentalist tells the participant what he or she is thinking; the rest of the audience are spectators who witness this process, but they are not involved in the effect. Conversely, macro effects attempt to involve everyone in the audience.