This study explores the psychological foundations of religious ritual systems. In practice, participants recall rituals to ensure a sense of continuity across performances, and those rituals motivate them to transmit and re-perform them. Most religious rituals exploit either high performance frequency or extraordinary emotional stimulation to enhance their recollection. Robert N. McCauley and E. Thomas Lawson assert that participants' cognitive representations of ritual form explain much about the systems. Reviewing a wide range of evidence, they explain religions' evolution.