There is no evidence to suggest that Ouija boards actually work; instead, scientists believe participants subconsciously guide the planchette towards letters as part of the idiomotor effect. As this is a subconscious effort, the game's participants do not know what is happening, which means they believe spirits are transmitting messages.
To test the idiomotor effect theory, scientists observed people using a Ouija board while blindfolded. Unlike when they were able to see the letters, the participants formed words that made no sense. If there were ghosts present and moving the planchette, the words would make sense. This demonstrates that the game's participants subconsciously move the planchette around the board to form messages they expect to see.
When the Ouija board was introduced to western society in the 19th century, it was a parlor game with no connection to the spirit world. During WWI, spiritualism experienced a revival and the game's manufacturers marketed it as a means of communicating with those who died in war. Because of this and the subsequent responses from religious organizations, Ouija boards were associated with the occult.
Hollywood depictions of the board, such as in the film "The Exorcist," encouraged the idea that Ouija boards can connect with ghosts and evil spirits . However, scientific evidence does not support this.