Neuroscience at Home: Why did pirates wear eyepatches?
Explanation Created by Brittany Bushnell (bnb233@nyu.edu)
The goal of this experiment and lesson is to explain dark adaptation, the ability for eyes to get used to seeing in the dark. When you picture a pirate, you immediately picture them wearing an eye patch. Most people assume that’s because they were often in battles and likely lost their eyes. In truth, it was a genius way to navigate around different parts of a ship. On deck, in the middle of the day, everything would be bright, but if you have to go downstairs below deck, it’s really dark. Rather than risk falling down the stairs, pirates would simply swap which eye their eye patch was over! The eye that was covered is already adapted to the dark conditions, so immediately the pirate would be able to see where they are and get down the stairs safely.
In this experiment, we’ll see just how helpful this trick would be by playing a game.
What you’ll need
Something to make an eye patch with. Get creative with this. Headbands, t-shirts, anything can work, but you want to make sure that it really blocks light from getting into the eye
A really dark (but safe to navigate around in) room.
Something for the kids to find.
How to do it:
Make your eye patch
Maybe you already have one from a pirate Halloween costume, in which case put on that whole costume! Might as well make this as fun as possible. There are a lot of different ways you can go with this. If you want to make something that’s a bit more of an involved craft project, you can follow these instructions to sew one. Or make one out of quite literally anything. For this to work best, you want to make sure the makeshift eye patch blocks as much light as possible from one eye (not both), and can easily be swapped between the eyes. It should also be pretty comfy. You want them to wear the eye patch for about 10 minutes before they do the actual experiment to give the eyes time to adapt
Hide your toy
“Hide” a toy in the darkroom. You don’t actually want to hide it anywhere that’s actually difficult. Put it somewhere that’s obvious when the lights are on, but if it was really dark you wouldn’t be able to see it. Keep in mind any light that might come in from the other rooms or hallways when first entering. You don’t want the hall light to shine on it and give the hiding place away.
Find the toy
After they have been wearing the eye patch for about 10 minutes, send the kid into the room to look for the hidden toy.
Make sure to close the door right behind you guys so it’s really dark. After a few seconds (just long enough to realize it really is dark and they can’t see anything) swap the eye patch to cover the good eye. Now the eye that was covered should be able to “see in the dark” and they should be able to find the hidden toy really easily.
Explanation
This is a great video that explains how the eye itself works. It’s really silly and I kinda love it.
There are two things happening that help us see in the dark:
First, the pupil dilates to allow more light to enter the eye.
Second, the eye changes what type of receptors it uses. Normally, we rely mostly on cone receptors to see things. That’s what lets us see really fine details, and colors. When it’s dark, our eyes rely on the rod receptors instead. It takes about 10 minutes for your eyes to make the change from cones to rods. If you want more details this website has a really thorough explanation of what’s going on when the eyes are adapting to the dark.
More experiments
If you want to play more with the differences between rods and cones (which I really suggest, cuz why not), start playing with how well you can see different colors in the dark. Even though the rods take over, cones are still active and certain colors are easier to see in the dark than others. If you have three things that are otherwise identical except for color (preferably red, green, and blue), have the kids see what color is easier to find.
Another fun thing is playing with where you can see best in the dark versus the light. Normally, we look directly at objects to see them because things in the periphery are lower resolution. That’s entire because of the layout of rods and cones. Cones are all clustered together in the center of the retina almost directly behind the pupil. That’s why we direct our pupils to whatever we’re looking for or at, it’s literally how we can see best. Have you ever had the experience of seeing something out of the corner of your eye in the dark, but then there’s nothing there when you look at it? That’s because the rods extend out to the side of the eyes and control most of our peripheral vision. At night, since they’re more active, you can see better out to the side than you can straight forward. You can also play with this one, but I’d be cautious with it if you have kids that get afraid of the dark.
Fun pirate history
There were a few famous female pirates! Anne Bonny and Mary Read were two incredibly powerful female pirates. They worked with Captain Jack Rackham, a famous pirate that is the guy that created this flag. Note, this video you might want to watch before showing it to kids. It’s all historical, but pirate history involves lots of murder and lawlessness.
Brittany is a senior Ph.D. student working in the labs of Dr. Lynne Kiopres and Dr. Tony Movshon. For her Ph.D. work, she’s researching abnormalities in brain function in adult non-human primates that have a visual disorder called amblyopia. This disorder occurs due to irregular visual input within the first two months of life, but the effects persist throughout a person's life.
The goal of her research is to identify the signatures of the disorder in irregular neuron responses throughout the visual system. She likes to use scientific outreach to expose tricks the brain uses all the time that we don't even realize and often take for granted. “Making experiments feel more like a game is a great way to get more people, especially kids, interested in science. “