# How Many Numbers Can You Remember?

## Abstract

Are you good at remembering addresses and phone numbers? How many numbers do you think you can remember? Try this experiment to test your digit span, the maximum number of digits that you can remember.

## Objective

In this experiment, you will test how many digits people can remember.

## Introduction

Are you good at remembering a phone number? Most people don’t even remember phone numbers anymore, and instead program them into their phones. There is a limit to the number of numbers, or digits, that most people can remember. The longest string of numbers that anyone has ever memorized is for the number pi (3.14159265…). Akira Haraguchi from Japan set a new world record by memorizing the first 100,000 digits on Oct. 3rd, 2006. That’s a lot of digits!

Our memory is a function of our brain, which processes and stores information from the world around us using our five senses: sight, sound, smell, taste, and touch. The brain integrates these experiences into a memory. For some people, certain senses create stronger memory than other senses. There are even people who never forget a smell, and become perfume makers!

In this experiment, you will test the memory of your participants. You will have them remember sequences of numbers that they hear you read. You will test them and compare how many they get correct. This will test the digit span of your volunteers. How many numbers will they remember?

## Terms and Concepts

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

• memory
• digits
• sequence
• random numbers
• frequency

## Questions

• How many digits can people remember?
• Will most people remember the same number of digits?
• Are there other factors affecting digit memory, like age or gender?

## Materials

• computer with internet
• index cards
• plastic baggies and a shoe box
• clipboard to hold data table

## Experimental Procedure

1. In this experiment, you will need number sequences for people to remember. Each number sequence should be composed of the numbers 0-9 and will be of different lengths. You will start with a sequence that is 2 digits long, and then 3, 4, or 5 digits until the volunteer can no longer remember a number. You can think them up yourself, or use this random number generator on the internet.
2. If you choose to use the random number generator, use your browser to go to http://www.random.org/nform.html and fill out the form so that it looks like this:
1. Then hit “Get Numbers” and a new page will appear with 7 listed numbers at the top. To get new numbers you do not need to fill out the form again, simply click the refresh button on your browser window, and voila! A new set of random numbers appears:

Here’s the 1st set I got:

And here’s the 2nd set I got:

4. On the first set of index cards, write two numbers on each card. These cards will be the first cards you read to your volunteer. Put them in a baggie labeled with the number 2.
5. On the next set of index cards, write three numbers on each card. These cards will be the second cards you read to your volunteer. Put them in a baggie labeled with the number 3.
6. On the next set of index cards, write four numbers on each card. These cards will be the third cards you read to your volunteer. Put them in a baggie labeled with the number 4.
7. On the next set of index cards, write five numbers on each card. These cards will be the fourth cards you read to your volunteer. Put them in a baggie labeled with the number 5.
8. On the next set of index cards, write six numbers on each card. These cards will be the fifth cards you read to your volunteer. Put them in a baggie labeled with the number 6.
9. On the next set of index cards, write seven numbers on each card. These cards will be the sixth cards you read to your volunteer. Put them in a baggie labeled with the number 7.
10. On the next set of index cards, write eight numbers on each card. These cards will be the seventh cards you read to your volunteer. Put them in a baggie labeled with the number 8.
11. On the next set of index cards, write nine numbers on each card. These cards will be the eighth cards you read to your volunteer. Put them in a baggie labeled with the number 9.
12. On the next set of index cards, write all ten numbers on each card. These cards will be the ninth cards you read to your volunteer. Put them in a baggie labeled with the number 10.
13. Collect your cards and organize them in a shoe box for easy transport and retrieval during your volunteer interviews.
14. You will also need a data table for your experiment. It should have a place to record the highest number of correct answers for each volunteer. Here is a data table where you put a check mark in the box for the participant each time they get the correct answers:
 Volunteer Info: Highest Number of Correct Answers: Name Age Gender 1 2 3 4 5 6 7 8 9 10
1. Find a research participant, and ask them if they will take a series of memory tests. Explain to them that you will read them a series of numbers slowly, and that then you would like them to tell you the numbers back in the same order that you read them.
2. Beginning with the 2 number cards, read the numbers slowly and let the volunteer respond. If they get the numbers right, put a check in the box and then move on to the 3 number cards. If they get these numbers right, then check the box and move on until the volunteer misses a number. If the volunteer misses a series, then do not check the box of your data table.
3. You will need to have a lot of participants for this study, so gather data from as many people as you can! When you are done, count up the total number of people who got each score on the test and make a frequency table:
 Score Number of participants with this score Percentage of participants with this score 0 1 2 3 4 5 6 7 8 9 10
1. Calculate the percentage of people who received each score. Dothis by first adding the total number of participants for each column, then divide the number of people receiving the score by the total number of participants in your study.
2. Analyze your data by making a histogram. On the left side of the graph (y-axis), write a scale for the percentage of people from zero to 100%. On the bottom of the graph, write a scale for the number of correct digits remembered from zero to ten. Then draw your results on the graph.