A Neuroscience Experiment You Can Perform On Yourself With Just A Mirror

Illustration for article titled A Neuroscience Experiment You Can Perform On Yourself With Just A Mirror

There are lots of DIY scientific experiments you can put to the test, without needing so much as a lab protocol. Not all of them are just kitchen chemistry, though. In fact, here’s a strange experiment a neuroscientist gave us to try out right now, on yourself.


In response to our query about the best at-home scientific demonstrations you can do, commenter and neuroscientist ResidentPony shared this odd little trick that your brain plays on itself.


How do you do it and, more importantly, what on earth just happened to you? Read on to find out:


Friendly neighborhood neuroscientist chiming in with my favorite experiment, and you don’t even need to be at home; you’ll just need a mirror.

Nut Graf / Clickbait

Did you know that the average person goes blind several times each second? And that your brain is lying to you?

One Weird Trick...

Here’s how to gather evidence that your brain can’t be trusted. Look into a mirror. Gaze deeply at your own eyes, admire your pretty irises. Focus on one eye. Then switch to the other. Then back. Read this in the voice of the Old Spice guy, but do it. Glance back and forth between your own eyes.

And... what the hell?! You’ll feel your eyeballs moving in their sockets, and you’ll definitely switch focus, but you won’t be aware of anything in the middle. There’s no blurry image of the bridge of your nose smeared by speed. You just tick-tock between focal points.

The eyes are doing their job just fine, thanks. But eyeballs have a flaw; for compactness and efficiency there’s really only a small spot on the retina which gives that excellent resolution patented by Apple. It’s called the fovea and it is tiny, able to observe only around 2 degrees of visual field. The rest of the retina is just filling in background info, the fovea provides sharp detail and rich color.

Explanation, Explication, and Expiation (for your eyes)

So we cheat. When we look at stuff, our eyes flick around to points of interest in a set of very fast movements called saccades. There’s a lot of meaning packed into that; we’ve got some awesome algorithms for picking the best points to examine, and for planning this superspeed movement, and we’ve got coprocessing circuitry for scanning stuff that is important to us, such as faces.

That’s right, I carry a high speed processor for your face.

(Image via Wikipedia; tracks indicate saccade movements when viewing a human face.)

Also there are different types of saccades, and some of them go bad in certain disease states and can be used as a diagnostic tool.

Here’s what happened in that mirror. The retina continued to send info but the eye was moving so the image would be blurred if we bothered to process it. But it’s not particularly useful data, since a. it’s blurred and b. it was picked up after leaving a point of interest and en route to another point of interest.

So your brain pretty much discards it.* And then hides the evidence so you don’t ever even realize that it’s chucking it out.

*It’s useful for some stuff, including error-checking and feedback for saccading, but it’s mostly suppressed from awareness.

Notice anything unusual when you tried it, perhaps something not unfamiliar to the videogame fans out there? There’s an explanation for that too:


There were a few... I dunno what you’d call them... frames? Where on top of not seeing my eyes move, the image of my eyes/face weren’t moving at all. The still image of my face was present while my eyes moved, basically.


That description sounds a lot like a phenomenon which often comes up in relation to saccades. Can I hazard a guess that this only occurred after you were well into the trick, maybe while switching very rapidly?

Because your experience sounds very similar to “chronostasis;” gamers know it as “lag.”


It’s another artifact of perception where a stimulus lingers for longer than its actual observation time.

Image: deradrian


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In further experimental notes, can also now confirm that staring at yourself intently in a mirror in a coffeeshop while patting at your own eye sockets will garner you some uncomfortable looks.