Today’s Wonder of the Day was inspired by Margo. Margo Wonders, “what is peripheral vision” Thanks for WONDERing with us, Margo!

Let’s do an experiment. Grab a friend or family member to help. Ready? Okay. Stare straight ahead. Now, ask your friend or family member to stand to the side. They should be where you can still see them without moving your eyes. 

Now, ask them to hold up any number of fingers. Can you see how many fingers they’re holding up? Ask your friend or family member to move slowly toward your central line of sight. At what point do you see them best?

You just tested your peripheral vision! This is side vision, or the ability to see things you’re not looking at directly. Peripheral vision helps people with many everyday tasks. When you’re eating with your family, do you have to look down directly at your plate each time you want a bite of food? No, of course not! Thanks to peripheral vision, you can see your plate well enough to pick up the food with your fork. 

When you look directly at a person or object, you’re using your central vision. When something is in your central vision, you’re able to notice many details about it. If it’s a person, you can tell whether they’re someone you know. If it’s an object, you can see its shape, size, color, and texture.

However, if something is in your peripheral, you won’t be able to see all these details. Sure, you can probably tell the difference between a person and a kangaroo using your side vision. However, you may not be able to tell the difference between two people. You might even mix up a kangaroo and a koala.

How exactly does peripheral vision work? The human eye contains millions of cells. The cells that help you see come in two types—cones and rods. Cone cells are sensitive to color. They work well when there’s plenty of light. Cone cells make up central vision. Peripheral vision uses rod cells.

Rod cells are good at picking up on movement. Have you ever seen something move from the corner of your eye? It may have startled you! There’s a good reason for that. Peripheral vision developed as a way for early humans to spot predators trying to sneak up on them. By alerting you to movement, the cone cells in your eyes are making sure you know there may be a predator nearby. 

Have you ever caught a tiger or bear trying to sneak up on you? Probably not! Most people don’t need to worry much about predators today. Instead, it’s more common for peripheral vision to help people avoid running into others when walking, riding a bike, or driving. Good peripheral vision tells people when another object is entering their proximity, which helps prevent accidents and collisions.

Other animals developed peripheral vision just like humans did. And some of them have a much wider line of sight! For example, goats can see nearly all around them. Their rectangle pupils give them a field of vision that’s 320-340 degrees! Chameleons, dragonflies, and mantis shrimp also have very large fields of vision.

Have you ever heard of tunnel vision? This is a condition in which a person’s peripheral vision is weakened. It can be caused by a concussion, eye strokes, and many other factors. In many cases, doctors can help prevent further vision loss with eyeglasses or eye drops.

Can you think of a time when your peripheral vision helped you? Did you escape a cheetah? Or avoid running into another kid on the playground? The next time you catch a glimpse of movement out of the corner of your eye, remember how helpful peripheral vision can be.

Standards: NGSS.LS1.A, NGSS.LS1.D, CCRA.L.3, CCRA.L.6, CCRA.R.4, CCRA.R.1, CCRA.R.2, CCRA.R.10, CCRA.SL.1, CCRA.W.2, CCRA.L.1, CCRA.L.2

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