What Is a Tachistoscope?

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  • Written By: Ray Hawk
  • Edited By: E. E. Hubbard
  • Last Modified Date: 04 December 2018
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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.


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Post 3

Aside from the negative aspects of this kind of machine, I'm surprised the positives aren't used more often in schools! It seems like it would be a very good thing to be able to speed read at more than twice the average rate. And if you look at what the navy does, it obviously has other applications.

Couldn't you get kids to learn how to identify plants and animals in biology in the same way? Get boy scouts to learn how to quickly identify venomous snakes, for example.

Are there any other places where this kind of technology is being used?

Post 2

@croydon - I was about to tell you that most research has shown that subliminal advertising doesn't work, but I looked it up to make sure and apparently there has been some recent studies of brain patterns that show that subliminal advertising does work a little. It lights up the brain anyway, even if you aren't aware of it.

Which is a bit scary, but I do believe that subliminal advertising is illegal anyway.

Post 1

I've never heard of this device before, but it seems like it's fascinating how much it could help people and harm them as well. I'd hate to be subjected to subliminal advertising whenever I was watching TV or using my computer. It's already annoying enough that there are devices out there like the Kindle which flash advertising across the screen.

I also heard Apple is thinking about developing technology that would lock your phone unless you interact with an advertisement. If they could use subliminal advertising as well, that would really suck.

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