31 minutes ago, Paladin said:

tachistoscope is a word and a device that I haven't heard or seen for decades, but certainly brings back memories. There was a time when they were popular and used for a wide range of things including training students to be speed readers and rapid recognition of objects.

They were also used in studies of subliminal perception where messages could be flashed at speeds below conscience awareness to influence behaviour, especially in marketing. A typical study would be to have a group of people watch a movie during which a message like "eat donuts" would be flashed on the screen subliminally . After the movie they would see how many people choose donuts.

Oh for those simple days.

Yes. These would team a device like a slide projector with a shutter control to limit the image display time.