A tachistoscope is a machine that is designed to flash a series of images very rapidly, sometimes so that they appear on a screen for only 1/100th of a second, to create subliminal imprinting in the mind. The technology and idea was invented by Dr. Samuel Renshaw, a 20th-century American psychologist who trained naval soldiers during World War II to rapidly recognize aircraft and ships on approach so as to avoid incidents of friendly fire and avoid delays in targeting enemy vessels. The system he developed came to be known as the Renshaw Recognition System (RRS), or Flash Recognition Training (FRT), and the concept has been applied to fields of subliminal marketing, advanced mental training, and psychological research since its inception.
While the machine was initially based on camera technology that employed a transparency projector or photography equipment that had a very rapid shutter speed, the process has now been automated into computer software. Software programs can flash images on a computer screen that are precisely timed and designed to enhance the ability to recognize certain shapes automatically. These systems are often referred to as Self-Help Subliminals, and the software can be customized to display whatever images or text messages the viewer wishes. Subliminal messaging of this type is a controversial subject when viewers are exposed to it involuntarily through media billboards and marketing broadcasts, but it has been shown to have some emotional effect on viewers that may predispose them towards an intended response. Research psychology holds a general consensus that such unconscious training of the mind has short-term, limited effects on behavior, though study into the process continues as it is seen to be of potential benefit in psychotherapy.
Renshaw patented the tachistoscope projector in 1946 and directed research using it at Ohio State University in the US aimed at topics such as speed reading. A small number of research subject students using the machine were able to increase their average reading comprehension rate from around 600 words per minute up to 1,416 words per minute with nearly 100% comprehension, though many other students had more modest increases in reading speed with the device. To accomplish this training, the device would flash images containing from five- to nine-digit numbers at 1/100th of a second, and the student was instructed to try to remember the numbers. Typically, 33 sessions of training that each lasted 30 minutes would be conducted before a reading speed test would be done to see if any change had occurred.
Later experiments with the tachistoscope were done on first-grade level children. The tests raised their reading level to an equivalent of third- or fourth-grade children. Engineers and scientists also took part in the training, with their reading speed increasing by an average of 52% to 85%. US Army and Navy adoption of the training for vessel recognition involved 285,000 cadets during World War II, and led to a RRS officer being stationed on board every US Navy ship that left port in 1943. After the training had become routine, some ships went through the entire war without once having a single incident where a friend or foe aircraft or ship was misidentified.
The theory behind how the machine was able to generate such amazing results is based on Renshaw's view on how the human eye sees. He dispelled with the myth that the eye is similar to optical devices like cameras or slide projectors taking rapid snapshots of individual images in the real world for processing by the brain. Renshaw theorized that, for human vision to be truly effective, most visual processing occurred subconsciously by memory and pattern recognition within the brain that went unnoticed moment by moment. His tachistoscope merely replicated this form of rapid visual processing, and tests with various segments of the population confirmed its effectiveness.