Engaging in actions such as knocking on a wood, throwing a ball, or holding a ball is believed to bring good luck or prevent bad luck, according to a study from the University of Chicago. These actions trace back to the ancient Celts and their reverence for oak trees, as they believed spirits resided in oak trees. The act of knocking is seen as waking up the spirits to request help for securing good luck or as a means to drown out conversations from bad spirits. This underlines the importance of taking action to feel like one is achieving a desired outcome of luck, rather than just thinking about it.