I see that this is your science project, so let’s talk about how you could answer your question scientifically.

Here’s how scientists, including you, would get started.

Phase 1: Find out what people already know about your variables: caffeine and reaction time. You might find some sources that tell you about just one or the other. Those are useful too.

Phase 2: Think about how you will test reaction time, your dependent variable. Think about how you will control your independent variable, caffeine consumption.

Here’s one way to test reaction time:
activity 1
Here’s another:
activity 2

You might have another way in mind. You just need to make sure that you will have something you can measure objectively, meaning that two different people will have the same answer. For example, “fast” means different things to different people. 2 seconds means the same thing to everyone, and if we are using the stopwatch correctly, we will get the same answer. WARNING! Any experiment that involves people has to be safe and ethical. Scientists have to go through a long process to get permission for experiments that involve people or other animals with a backbone. You will need to get permission from your teacher. Your teacher may decide that having people consume caffeine is not a good idea. You might want to have a backup plan. This happens to scientists all the time. We want to do plan A, but don’t have enough money. We think about doing plan B, but something doesn’t work. Plan C would be cool, but we can’t get permission. We figure out a plan D.

Successful scientists don’t quit. We find new ways to solve problems. You may want to go back to your research on reaction time and see what other variables influence reaction time and talk to your teacher about what will work. Think about any dangers or other problems you might have in measuring your variables.

Phase 3: Write out your plan in so much detail that another person could follow it without you. You can use this later as the “Methods” section in your poster or paper.
What will you do?
What will you measure?
You may want to make up a table of form for recording your data.

Phase 4: Gather up your materials and test subjects (people) and do your tests, recording all of your results carefully.

Phase 5: Analyze your data. Graphs can be very helpful. You might want to figure out the averages for different groups of people.

Phase 6: Report your data.

Let’s just focus on Phases 1 and 2 right now. Feel free to check back for more help.

This is a great question that you could test in your science project! For example, you could have a visual and/or audio test and get people to hit a button when they see and/or hear the signal. You could perform this test with several people, at the same time of day, and then do the same test another day, but give them coffee beforehand.

To test the effect of coffee, you could also give them coffee right before the test, 10 minutes before, 20 minutes before, 30 minutes before, 60 minutes before the test.