Put Your Peripheral Vision to the Test
Did you know we use our side vision for many daily activities, like riding a bike, reading or playing basketball? Few people realize they are even using it. Our survival once depended on the quick response of our peripheral vision. A detailed picture, created by our central vision, is only useful in situations where time allows us to focus on the details. But our side vision can help us avoid dangers quickly. In this activity, you will find out how specialized our peripheral, or side vision, is.
When you look at something, you use central vision to focus on the details, and peripheral (or side) vision to gather information about the surroundings.
The diversification between central and peripheral vision starts in the back of our eyes where we have two types of light-sensitive cells, called cones and rods. Our central vision uses an area densely packed with cones. Cones are sensitive to color and need ample light to function well. Our peripheral vision uses rods and almost no cones. Rods are sensitive to movement and quickly pick up changes in brightness. They function well in a broad range of light conditions.
The diversification continues as signals travel to the brain. Some signaling cells are sensitive to color but not so much to contrast, while other cells signal faster and respond to low-contrast stimuli. Even in the visual cortex of the brain, more neurons will analyze a stimulus picked up by our central vision compared to the same stimulus picked up by our peripheral vision. All of this leads to our color-sensitive, high-resolution central vision and our fast-working, movement-sensitive peripheral vision.
With all this information on our visual system, will you be able to predict what your side vision will perceive? Do this activity to find out!
- Cardboard or foam board:
- One thirty by sixty centimeter board, or
- Two thirty by thirty centimeter square boards held together with tape
- Metric ruler, a thirty-centimeter-long ruler works well
- A string, about fifty centimeters long
- A push pin
- Stack of scratch paper or a newspaper
- Scissors or craft knife
- Disposable cup
- Glue or clear tape
- Construction paper or paper and markers; we suggest red, yellow and green, but other colors work too
- The following steps will help you build a vision protractor.
- If you have two thirty by thirty centimeter boards, tape them together so they form a thirty by sixty centimeter board.
- Put your board on a flat surface in front of you with the long side closest to you. Find the middle of the long side; this should be thirty centimeters from each corner. Mark this place with a pencil. You will soon put a push pin in the board at this place.
- Place a newspaper or stack of scratch paper underneath the board to protect your surface underneath, and stick a push pin into the board on the indicated place.
- Tie one end of the string around the pencil. Tie the other end to the push pin so the string is exactly thirty centimeters long.
- Use the attached pencil to draw a half-circle with a radius of thirty centimeters.
- Shorten the string until the distance from the pencil to the push pin is two centimeters and draw a small half circle—within the larger circle—with a two centimeter radius.
- Remove the pencil, the string and the push pin and cut along the big and small lines. You should be left with what looks like a rainbow. The big half-circle is the outer edge of your vision protractor, the small half-circle cut-out makes a place for your nose.
- Pin the push pin near the outer edge of the protractor, directly across from your nose hole. If the protractor were a rainbow, this point would indicate the highest point of your bow. Before you do so, be sure the pin is not poking anything underneath! This push pin will serve as a focus point, or a point to look at while you perform each test. Tape some scratch paper around the point of the push pin so it does not accidently poke any items or people.
- Attach a disposable cup on the bottom of the protractor, near the center. This will serve as a handle.
- If you started with two thirty by thirty centimeter boards, you might need to attach reinforcement on the bottom side so the two pieces of the protractor stay flat. You can use the scrap pieces of board for this.
- Your vision protractor is now ready to use.
- You now need to create some shapes to look for before you can start the test. To do so, take three different colored sheets of construction paper. We suggest trying red, green and yellow, but other colors will work too. Cut out two rectangular strips of ten by two centimeters of each sheet, for a total of six strips. If you do not have construction paper, you can use white paper strips and color them with markers. Note that each strip needs to be one uniform color.
- Take one strip of each color and cut off the corners so the top of the strip forms a triangle. You should now have three strips like this. Leave the other three strips as rectangles.
- If your strips bend over when held up, you can reinforce them with additional paper, craft sticks or straws.
- Hold the vision protractor up to your face with your nose in the center nose hold. The protractor should be held horizontally during the test, so the half-circle stretches out in front and to the side of you. Keep your gaze on the push pin during the test.
- Your helper will hold one of the paper strips against the outer edge of the vision protractor so two centimeters stick straight up above the vision board. He or she will hold it on your left, near the long straight edge of the protractor. While you continue looking at the push pin, the helper will move the strip slowly and evenly along the curved protractor edge toward the middle. How far do you think the helper will need to move the strip before you observe something is there? Do you think the helper will need to move it farther before you can detect the color and/or shape of the strip? Much farther, or just a little bit?
- Perform the test. Have the helper stop moving as soon as you can first detect the strip. Can you detect the shape or the color of the object, or can you just tell there is something there? Remember to keep your eyes on the push pin at all times during the test.
- Have your helper keep moving the object along the edge toward the center of the protractor. Ask the helper to stop again as soon as you can detect more detail, like the color or the shape. What can you detect first, color or shape, or are you able to detect both at the same time?
- Repeat the previous step until you can detect the shape, as well as the color of the object. Can you detect details of the object at this location, or does it need to be moved closer to the push pin to detect details?
- Now let the helper choose a different strip. Do you expect the outcome to be different? Can your peripheral vision detect one color earlier than another?
Extra: Repeat the test in a darkened room after allowing your eyes to adjust to the new situation. Do you expect the results to be different, and if so, how do you expect your outcome to change?
Extra: Repeat the test, but now, ask the helper to wiggle the strips while he or she is moving them along the side of the protractor. Do you expect the outcome to be different, and if so, how do you expect it to change?
Extra: Write a letter or number with pencil or pen on the top two centimeters of the strips. When do you think you will be able to read the letter or number? Perform the test to find out.
Observations and Results
You probably quickly observed something appearing in your side view, but could only later tell the color, and even later, identify the shape. This is what is expected.
Our peripheral vision is quick at detecting that something enters our field of sight, but it is weak at distinguishing color, shape or detail. This is because fewer and different cells in our eye and brain are activated when ‘seeing’ an object with our peripheral vision than when ‘seeing’ the object with our central vision.
Our peripheral vision has evolved since the time of our ancestors to serve us well. It allows us to escape from an approaching danger quickly in dim, as well as bright, light and is very good at noticing movement. This explains the results of some of the extra instructions: dim light conditions still allow you to quickly detect the object with your peripheral vision, and you notice the object even faster when the object is wiggling. Our ancestors did not need to identify the type of danger instantly. To ‘see’ color, shape and details, they could wait until ample light was available, and use their central vision to study a relatively still object.
Ask an Expert
- The Retina, from Neuroscience For Kids
- When a flashing light shows more, from Scientific American
- Now You See It, Now You Don't. Test Your Peripheral Vision, from Science Buddies