A tachistoscope is an instrument that shows you something, such as a word, a number or a picture, for a very short and exactly controlled time, and then takes it away. The name is built from Greek roots meaning "swiftest" and "to view". Psychologists have used the device since the nineteenth century to study how much a person can perceive in a single glance, and trainers later borrowed it to teach people to recognise shapes and words quickly.
Today the cabinet-sized machines are museum pieces and the same job is done by a screen. Flash-recognition drills in reading apps are tachistoscopes in software. This guide covers where the device came from, how the training works, and what it can and cannot do for your reading.
Who invented the tachistoscope?
The first tachistoscope was described by the German physiologist A. W. Volkmann in 1859. In the 1880s James McKeen Cattell built a related instrument, the gravity chronometer, at Wilhelm Wundt's psychology institute in Leipzig. The historian Benschop (1998) traces this early family of devices and makes the point that "the tachistoscope" was never one standard machine: each laboratory assembled its own.
The mechanics changed over the following century, while the idea stayed the same:
| Period | How the flash was produced | Typical use |
|---|---|---|
| From 1859 | A falling or rotating screen with a window in it passes in front of the stimulus; the size of the window sets the exposure. | Laboratory studies of perception. |
| Mid-twentieth century | A slide projector fitted with a camera-style shutter, and later lamps that switch on and off very quickly. | Recognition training, classroom reading programmes, research. |
| From the 1990s | A computer screen that draws the stimulus for a set number of frames. | Research, and later reading and brain-training apps. |
The move to screens was checked rather than assumed. Hutner and colleagues (1999) compared a conventional cabinet tachistoscope with a computer monitor for exposures of 14, 29 and 43 milliseconds and found that people's error rates were similar on both.
How was the tachistoscope used to train aircraft recognition?
The best-known application came during the Second World War. Samuel Renshaw (1892–1981), a psychologist at Ohio State University, used tachistoscopic flashes of silhouettes to train United States Navy personnel to tell friendly aircraft and ships from enemy ones at a glance. The reasoning was that a lookout rarely gets a long, steady view, so recognition should be practised under the same time pressure, as a judgement of the whole shape rather than a check of its details. Renshaw published his laboratory work on the method in 1945.
After the war the same equipment moved into classrooms. By the late 1950s tachistoscopes were being used to teach reading; Brown (1958) describes the practice in a journal for reading teachers. Flash training became a fixture of commercial speed-reading courses, and the claims made for it grew much faster than the evidence.
How does tachistoscope training work?
Every flash-recognition drill follows the same loop:
- A mark shows you where to look.
- The item appears there for a fixed time, then vanishes.
- You report what you saw, by typing, writing or saying it.
- You see whether you were right.
- Once you are reliably right, the exposure gets shorter or the item gets longer.
The point of the short exposure is to remove the option of a second look. In ordinary reading your eyes rest on a word for roughly 200 to 250 milliseconds before jumping on. A flash of that length or less gives you one fixation's worth of information and no chance to inspect the word letter by letter, so you have to recognise it as a whole. See how your eyes move when you read for what happens during those pauses.
Does tachistoscope training improve reading?
It improves flash recognition. People get better at the drill with practice; that much is not in doubt. The harder question is transfer: whether being quicker at isolated flashed words makes you quicker at reading connected text.
We found no solid evidence that it does, and there are good reasons to expect little. The 2016 review of speed reading by Rayner and colleagues concludes that reading speed is limited mainly by language processing, meaning how fast you recognise words and fit them into the meaning of a sentence, and that pushing speed far beyond your normal rate costs comprehension. A skilled adult reader already recognises common words within a single fixation, thousands of times a day. Flashing short, familiar words rehearses something you do well already.
A tachistoscope trains you to recognise a word from one brief look. It does not train understanding, and understanding is what sets your reading speed.
What a flash drill is reasonably good for:
- A short burst of full concentration. You cannot do it half-attending, which makes it a useful way to begin a reading session.
- Practising whole-word recognition in a language you are learning, where words are not yet familiar shapes.
- A clear, honest score that shows practice effects within days.
What it will not do is double your reading speed, enlarge the amount of text you see per glance or improve your eyesight. For the broader picture, read does speed reading work?
How does the Tachistoscope drill in Tachi work?
Tachi's version follows the classic loop. A fixation dot appears for a little over half a second, a single word flashes in its place, and you type the word back. A round is ten words, and the result shows how many you got right. You choose two things before you start:
- Word length: 3, 4, 5 or 6 letters in English.
- Level: 1 to 10. The flash lasts 200 milliseconds at level 1 and then 150, 125, 100, 75, 50, 30, 20, 15 and finally 5 milliseconds at level 10.
Why the shortest flashes are limited by your screen
A screen cannot show an image for less than one refresh. A 60 Hz display redraws about every 16.7 milliseconds and a 120 Hz display about every 8.3 milliseconds. So on a 60 Hz screen the 15 and 5 millisecond levels both show the word for a single frame, roughly 17 milliseconds, and look the same; on a 120 Hz screen the 5 millisecond level is really about 8. Longer flashes are rounded to whole frames as well. Tachi times each flash from the moment the word is first painted so that the shortest ones are not skipped, but it cannot beat the hardware. Read the top levels as "one frame", not as a laboratory measurement.
A tachistoscope practice plan
One to two minutes a day is enough. Longer sessions mostly measure fatigue.
- Find your level. Start with 4-letter words at level 1 (200 ms). Play one round of ten words.
- Move up on 9 or 10 correct. Go up one level for the next round. On 6 or fewer, go down one. In between, stay where you are.
- Lengthen before you shorten. When you reach about level 6 (50 ms) with 4-letter words, switch to 5 letters and drop back two levels, then repeat with 6 letters. Longer words are closer to real reading than ever-shorter flashes.
- Stop at two or three rounds. Keep your eyes on the dot and resist guessing from the first letter; a wrong answer tells you more than a lucky one.
- Then read real text. Five to ten minutes of ordinary reading, or paced reading in an RSVP reader, is where the practice that counts happens.
The drill pairs naturally with the Schulte table as a two-minute warm-up. The full ten-minute routine is on the How Tachi works page, and how to read faster covers the habits that make the larger difference.
Frequently asked questions
What does the word tachistoscope mean?
It combines the Greek tachistos, meaning swiftest or very fast, with a root meaning to look or to view. The name describes what the instrument does: it lets you view something for a very brief moment. The related adjective, tachistoscopic, describes any presentation made this way, whatever the equipment.
Are tachistoscopes still used today?
The mechanical and projector-based machines have largely been replaced by computers, which took over in research laboratories during the 1990s. The method itself is still common: experiments on perception and attention show stimuli for controlled fractions of a second, and flash-recognition drills in reading and training apps work on the same principle.
How fast can a person recognise a flashed word?
It depends on the word, its size and contrast, and what follows it on the screen, so there is no single figure. For comparison, the eyes normally rest on a word for about 200 to 250 milliseconds during reading, and flash drills go well below that. On a phone or laptop the practical floor is one screen refresh, about 17 milliseconds at 60 Hz.
Is tachistoscope training the same as RSVP reading?
No. A tachistoscope drill shows one isolated item and then stops so you can report it; it tests recognition. RSVP shows the words of a real text one after another at a steady rate, so you also have to follow the meaning. The first is a perception exercise, the second is a way of reading.
Can tachistoscope training improve my eyesight?
No. Flash drills practise attention and recognition; they do not change how sharply your eyes focus and they do not correct short-sightedness, long-sightedness or astigmatism. If text looks blurred, or reading gives you headaches or double vision, see an optometrist instead of relying on any exercise.
Sources
- Benschop (1998). What is a tachistoscope? Historical explorations of an instrument. Science in Context, 11(1), 23–50
- Musée L, Université catholique de Louvain. Tachistoscope (museum object note, in French)
- Renshaw (1945). The visual perception and reproduction of forms by tachistoscopic methods. The Journal of Psychology, 20(2), 217–232
- Brown (1958). Teaching reading with the tachistoscope. Journal of Developmental Reading, 1(2), 8–18
- Hutner et al. (1999). Comparing visual perception on conventional cabinet tachistoscopes and computer monitor tachistoscopes. Behavior Research Methods, Instruments, & Computers, 31(3), 400–409
- Rayner et al. (2016). So much to read, so little time: How do we read, and can speed reading help? Psychological Science in the Public Interest, 17(1), 4–34