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Your brain does a lot to smooth out your visual experience of the world… including the closest thing we have to time travel.

Hosted by: Hank Green
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Sources:
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[INTRO ♪].

You know how some videos can be super disorienting, like if whoever’s holding the camera just can't keep their hand steady? Or maybe you’ve seen the Blair Witch Project in all of its shaky cam glory.

Having your vision move around a lot can get downright nauseating. But also, your eyes move all the time to get a complete picture of what's going on in front of you. So why doesn’t day-to-day life feel like a poorly-calibrated first-person video game?

Well, your eyes and brain cover up that mess by doing some really weird stuff—even changing how you perceive time. Your eyes move a lot. Like, you might notice just how quickly they jump around when you're reading.

Scientists call those jumps saccades. Each one can take up to a hundred milliseconds, depending on how far your eyes need to turn. But instead of showing you blurry motion all the time, your brain kind of just skips those moments.

One way psychologists know this is because of a certain kind of vision experiment. If you time the movement of the object to be exactly during a saccade, people have a hard time noticing. One study asked people to flip a switch when they saw an image jump while having their eyes tracked.

The researchers found that if the image jumped about 10 milliseconds after the start of a saccade, people didn’t notice— as long as their eye movement was about 3 times bigger than the image’s movement. Other studies had people move their eyes to focus on an array of dots that appeared in their peripheral vision. If the pattern of those dots changed during the saccade, the participants had trouble noticing the change.

But if the participants kept their eyes still and the dots moved to where they were looking, they noticed a pattern change more frequently. You can sort of test this yourself, too. Just look in a mirror and move your eyes—you'll never actually see your eyes in motion.

All of this is the study of transsaccadic memory, which is basically your brain's short-term storage of all the visual information it’s taking in to form a complete picture of the world, like puzzle pieces. Your brain doesn't just leave a hole in your vision during saccades. It fills in that gap in with what's around it, chronologically.

And what's really weird is that seems to draw more from what you see right after the jump. I'll let that sink in. How can your brain show you things that are happening in the future, even if it’s just a fraction of a second?

Well, it has to do with the fact that you don’t process things instantaneously. Your brain filters everything that your senses detect. And your sense of time passing can also change based on what you're doing and focused on.

This is an illusion called chronostasis, which means "stopping time" in Greek. You can see it yourself if you've got a watch with a ticking second hand. If you look away from the watch and then back, sometimes the second hand will seem to pause for a little bit too long before ticking again.

Basically, there seems to be a tiny delay between your eyes receiving light information from the watch and your conscious visual perception of the watch. When you've got a saccade to fill, it's like your brain puts a rush order on the next bit of information from your eyes—that’s the “seeing the future” part. And then it rests for a second.

Well, not a whole second. Part of a second. In some studies of the chronostasis illusion, subjects had their eyes tracked.

When they focused on a specific point on a screen, a 4 second timer started. But here’s the catch: that timer would vary how long it would display the first number by a few hundred milliseconds. Then subjects were asked whether that first number was displayed for a longer or shorter time than the rest.

And the researchers found that they could shorten that first second by about 120 milliseconds on average before people would say it seemed shorter. In other words, people were overestimating how long that first second took by about 120 milliseconds. Their mind’s eye was holding onto that image of a number 1 just a little longer.

So… kind of like time travel! We don't have a complete biological explanation for this phenomenon. It's hard to get deep into the visual systems of living humans, and monkeys and rats can’t exactly report their perception of time.

But we know that the illusion happens whether a person voluntarily moves their eyes or does it reflexively because something appears in their peripheral vision. This suggests it's a very low-level process in the brain. Researchers think it could be part of a signal coming from the superior colliculus, which is a brain region involved in processing vision and unconscious movement of your eyes.

But this is really just a guess based on what seems to fit the data we have so far. And, to make things even more complicated, the chronostasis illusion doesn't just happen with vision. People have similar experiences with other senses, like touch or hearing.

Like, in experiments kind of like that timer study where participants reach and grab a vibrating handle, they overestimate how long it vibrates at different frequencies after they make contact. Or people will overestimate the length of a period of silence if tones [tone on left] switch from one ear [tone on right] to the other. So scientists have a bit of a mystery to unravel when it comes to time-stopping illusions.

At the very least, we know that our perception of time isn’t consistent—maybe to help make the world a little less disorienting. But no need to break out the flux capacitors or the failsafe machines just yet. Thanks for learning about these brain mysteries with us here at SciShow Psych, and thanks especially to our patrons on Patreon.

If you want to support us as we make all these videos and share how fascinating our universe is, you can go to patreon.com/scishow. [OUTRO ♪].