"If the grace of God miraculously operates, it probably operates through the subliminal door."
William James, psychologist
In 1859 German doctor Alfred Wilhelm Volkmann (1800-1877) built the first tachistoscope, a device capable of influencing subliminal thought by flashing pictures for as little as ten milliseconds. Using mechanical shutters similar to those used in cameras, Volkmann exposed people to images of emotive words. The people would not notice them consciously, yet subconsciously they would project the corresponding emotions onto a subsequent image.
However, because of their mechanical nature the shutters can't be controlled with perfect precision, and hence flashtube tachistoscopes were developed. Tiese use mirrors in a large box and a small lamp that goes from complete darkness to extreme brightness
and back in a few milliseconds. The person looking into the viewing hole gets the impression that every image appears in the same spot, which allows the person conducting the experiment to show not only the "subliminal" and target images, but also an unrelated, meaningless picture in between, which serves to disrupt the link between conscious and subconscious thought even further.
While tachistoscopes were used to help World War II fighter pilots distinguish the contours of enemy aircraft, and subliminal messages are employed in advertising, doubts remain as to whether this technique actually achieves any tangible success.
