Race Your Reflexes: Experimenting with reaction time

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We use our reflexes on a daily basis: catching a ball that is flying toward you, dodging obstacles (like toys on the floor), or grabbing a plate before it crashes to the floor.

What’s going on in our bodies when we have to think fast?

This experiment tests reaction time by catching a falling ruler and measuring how long it takes your body to react in order to catch it. It covers reaction time, reflexes, measurement, and analyzing what factors might impact performance (like being distracted or tired).

It’s a simple set-up for an engaging and exciting STEM experiment!



How to make the Race Your Reflexes Reaction Time STEM experiment

Supplies you will need

For this experiment, you’ll need:

Supplies needed for the Race Your Reflexes Reaction Time STEM experiment

Before you start

Please watch all fingers when catching the ruler or yardstick. Check it out for any splinters or sharp edges that may hurt your hand when catching it.

Instructions

Here is how to do this experiment with your child:

Step 1: Make the strips for the ruler

Measure 4″ of red, yellow, and green construction paper and make them approximately 2″ wide. Cut out the strips of paper.

Rectangle drawn on the construction paper that is 4″ long and 2″ wide
Cut out rectangles for each piece of construction paper

Step 2: Tape the strips to the ruler

Next, we’re going to tape the strips of paper to the ruler. They should go in order of green, yellow, then red.

Start at the top of the ruler and wrap the green construction paper around the ruler. Be sure to tape the paper directly to the ruler (instead of taping the paper to the paper), then wrap the paper around and tape it again. We want to make sure we do not pull the paper off when conducting the test.

Add the yellow under the green paper, and finally the red paper under the yellow.

The entire ruler should be covered with three different colors of construction paper.

Taped construction paper pieces on the ruler

Step 3: Drop the ruler to test reaction time

Have someone hold the ruler with the red construction paper at the top.

Keep your index finger and thumb close together at the base of the ruler (on the green side).

It’s time to drop the ruler and test your reaction time! See how quickly you can catch the ruler between your index finger and thumb by pinching it. Did it land on the green (fast), yellow (medium), or red (slow)?

Reaction time test, before
Reaction time test, after

The STEM behind the Race Your Reflexes Reaction Time experiment

This experiment teaches:

  • Reaction time
  • Measurement
  • What factors change performance

How it works

This experiment demonstrates reaction time and how we can measure it using a few simple tools.

In this experiment, we use a simple ruler and some construction paper to indicate a “fast”, “medium”, and “slow” reaction time. Having a friend hold the ruler, you hold your fingers at the base of the ruler and wait for it to drop. Once the ruler is dropped, you must pinch the ruler as quickly as you can.

This experiment gives you the opportunity to talk about how our body processes information in order to catch the ruler quickly, measure and analyze the data from the experiment, and test to see what factors can change your reaction time.

Reaction time

Reaction time tests demonstrate how the brain receives information, processes it, and then sends signals to the body to respond. This helps us understand the basic concept of how our nervous system functions.

When you’re testing reaction time (like catching a falling ruler), your senses (in this case, sight) receive information from the outside world. Your eyes see the ruler moving. This information travels along nerves to your brain. Your brain then processes the information:

  • It recognizes the object (a ruler).
  • It understands the movement (it’s falling).
  • It decides what action needs to be taken (catch it).

Once your brain processes the information, it sends a signal back down the nerves to the appropriate muscles in your body (the hand and arm, in this case).

Your muscles then receive the signal and contract, causing you to move your hand and catch the ruler.

All of this happens in a split second!

Measurement

A reaction time experiment involves measuring how long it takes someone to respond to something, collecting the data, and analyzing it. In the case of this experiment, we are testing how quickly we can catch a falling ruler.

Let’s start with teaching our kids how to measure using this experiment. Before we started the experiment, we added sections to the ruler indicating reaction time (fast, medium, slow). As you experiment, take simple measurements to see where your hands are on the ruler after you drop it. It’s as simple as that!

Next, we want to collect the data. Have your child write the measurements down (if they’re able to). Decide ahead of time what factors you want to collect: the person’s name with their reaction time, the time of day (to see if reaction time changes based on the time), the person’s mood (how does mood affect reaction time?), and so on.

Last, analyze the data. Did you have a faster or slower reaction time first thing in the morning? When you were stressed out about something, did that affect your reaction time? See how many conclusions you can draw from the data you collected! Even better: can you find some areas in which your data collection was lacking? What other data points could you have added to the collection phase?

What factors change performance

In this experiment, we can also take a look at how different factors (like fatigue, distractions, or even the time of day) can affect reaction times.

Here are a few common facts that can affect performance:

  • Fatigue: If you’re tired, your brain and body may not respond as quickly.
  • Distractions: Loud noises, bright lights, or even just thinking about something else can slow down your reaction time.
  • Mood: If you’re feeling stressed or anxious, your reactions might be slower.
  • Practice: With repeated practice, your brain can become more efficient at processing information and sending signals to your muscles, leading to faster reaction times.



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