Flashing words fast for the human mind to understand

Thread Starter


Joined Nov 4, 2008
I am working on a design. It consists of 6ea 7 segment displays that has numbers manually set with some bcd switches and some CD4511 decoder drivers.
I posted earlier a picture of the deisign. The design is working as I planned.
I would like to add another feature. This feature is to turn off the numbers and turns some words for a short time. Once the switches are manually set they remain in view for about 45 minutes, with no changes. I am aware that if words or pictures are visible for a very short time the human mind can see it.
So my question is: How fast must is change from the normal view of the numbers to the words. My second question is, Is it lawfully okay to do this.
I remember this thing happening in movie theaters so the people there would be encouraged to get goodies from the theater.
Thanks for looking


Joined Mar 31, 2012
What's your objective in doing this?

As to the legality, that depends in what your objective is in doing this (and where in the world you are doing it).

As far as I know, no one has ever established that subliminal messages have the ability to influence people's thoughts or actions in any way, although there are claims that they can trigger people to do something that they were already planning to do anyway -- but what the hell does that mean?

The whole movie theater story was a hoax. In 1957 James Vicary (the person that introduced the term "subliminal messaging") was trying to attract customers to his failing marketing company and claimed that flashing "Eat popcorn" and "Drink Coca-Cola" for just 1/3000th of a second during of a movie at a theater resulted in a nearly 20% of one and 60% of the other. But later he admitted that his claims were completely made up and that no experiment had ever even been conducted.

Consider that a movie at a theater (in 1957) was projected at 24 frames per second. So flashing something for just 1/3000th of a second would have required special equipment be used. The movie theater in question asserted that no experiment had ever been conducted there and since they would certainly have been aware of the special equipment being used in their theater, it's a pretty safe bet that they are correct.

Glenn Holland

Joined Dec 26, 2014
This is commonly known as "Tachistoscopy" and it has been used for displaying text and still images for the purpose of enhanced reading comprehension.

The concept is to display entire sentences one word at a time so the viewer does not stare and scan the text or the text around it. It does allows the person to read faster and memorize the phrases You might call this a form of serial data transmission VS parallel transmission.