Chronostasis

How it works

Your eyes do not glide from one place to another. They jump. Each jump is called a saccade, and it takes between 20 and 200 milliseconds⁴. During the jump the image smears across the retina. The brain switches vision off for that time, so you never see the smear. This is called saccadic masking².

That leaves a hole in your visual record. The brain fills it in a simple way. It takes the first stable image after the jump and stretches it backwards in time to cover the whole saccade¹. You experience the new scene as if it had been there since before the eyes moved.

Usually this is harmless. But if the first thing you land on is a clock, the second hand you land on gets stretched too. It seems to sit still for longer than a second. Then it ticks normally. That is the stopped clock¹.

The effect was measured in 2001 by Kielan Yarrow and colleagues at University College London⁵. They found that the first image after a saccade was judged to last longer than it really did, and that the stretch grew with the length of the eye movement⁵. Similar effects have since been found for hearing, when attention shifts from one ear to the other, and for touch, when a hand reaches for an object¹.

How common it is

Chronostasis is not something researchers count in a population, because it happens to everyone with working eyes each time they jump to a new fixation point⁵. It is easy to miss because it only stands out when the first thing you look at is something moving in a regular, countable way, like a clock hand.

Try it

1. Find an analogue clock with a second hand that ticks once a second. A digital clock showing seconds also works.
2. Look away from it, somewhere off to one side.
3. Snap your eyes back to the clock in one quick movement.
4. Watch the first tick. Sometimes it seems to take longer than the ones that follow.
5. Repeat with a larger eye movement. The freeze is longer.

The effect is easier to notice than to test, because you cannot look at the clock without moving your eyes to it.

Is it a problem?

No. Chronostasis is a normal gap-filling habit of the visual system, not a sign of anything wrong with your eyes or your sense of time¹². It happens to everyone and is noticeable only in the specific case of glancing at a ticking clock.

There is nothing to watch for here. It is unrelated to memory loss, blackouts, or missing stretches of time, and it lasts a fraction of a second, unlike those experiences.

History and culture

Many people have noticed the stopped clock on their own. The XKCD comic “Visual Field” mentions it in its hover text³.