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The Bouba-Kiki Effect

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Have you ever wondered if some shapes have certain "sounds" to people, even if they have different native languages? For example, does everyone match certain physical characteristics, like sharpness or roundness, with certain sounds? Are there certain human sounds with meanings that can cross the language barrier? In this science project you will investigate this by testing the Bouba-Kiki Effect—will it turn out that abstract visual properties can be linked to sound?


Areas of Science
Time Required
Very Short (≤ 1 day)
Material Availability
Readily available
Very Low (under $20)
No issues

Sara Agee, Ph.D., Science Buddies


Investigate whether people match certain symbolic characteristics, like sharpness and roundedness, with certain sounds.


One of the most amazing things humans can do is use language to communicate. Humans have evolved the ability to use language over many thousands of years, resulting in many languages being spoken around the world today. How did our ability to use language evolve? Where did the first use of language come from?

One idea is that the first use of language represented sounds that became linked to concepts through usage. Eventually these meaningful sounds became more complex in structure and more diverse, creating more complex language. This idea brings with it a major question: Were the first sounds arbitrary and random, or were they consistently applied to certain concepts or symbols? You might think that since modern languages have different origins, that different random associations with sounds could be at the root of these differences. However, a psychological phenomenon called the Bouba-Kiki Effect shows a different possibility.

In the Bouba-Kiki Effect, people are shown a pointy picture or a curvy picture and asked to identify it as "Bouba" or "Kiki" even though those are both non-sense words. A surprising number of people, regardless of language, identify the rounded shape as "Bouba" and the pointy shape as "Kiki" even though they had not been told what the words might mean. Even very young children make the same identification most of the time. What does this mean? Is this evidence of a human predisposition to associating certain sounds with abstract shapes and concepts?

Two irregular shapes with sharp and rounded edges
Figure 1. Most people, when asked, will say that the shape on the left is "Kiki" and that the shape on the right is "Bouba" even though they may not speak the same language and have not been told what the two words mean.

While the deeper meaning behind the Bouba-Kiki Effect is being debated in coffee shops at colleges and universities around the globe, you can turn it into a nifty science fair project. In this human behavior science project, you will make your own set of Bouba-Kiki flash cards and then test volunteers with your flash cards to see if you observe the Bouba-Kiki Effect. Will you see it, or will you have the results of a 50-50 random chance event?

Terms and Concepts



To find out more about the Bouba-Kiki Effect, visit the following websites:

For help creating graphs, try this website:

  • National Center for Education Statistics, (n.d.). Create a Graph. Retrieved June 25, 2020.

Materials and Equipment

Experimental Procedure

  1. First, you will need to design your stacks of index cards. Start by making two stacks, each having 10 index cards.
  2. On one stack of cards, draw pointy, abstract shapes like Figure 2 below.
An irregular star-shape with seven points
Figure 2. On one stack of 10 cards, draw a pointy shape like this one on each card.
  1. On the other stack, draw round, bubbly shapes like Figure 3 below.
An irregular shape resembling an amoeba
Figure 3. On the other stack of 10 cards, draw round, bubbly shapes like this one on each card.
  1. Shuffle your two decks of cards together a few times, to make them mix at random.
  2. In your lab notebook, make a data table like Table 1 below. You will be writing your results in the data table in your lab notebook.
    1. Notice that the answers your volunteers will give you are not REALLY correct or incorrect, since "Bouba" and "Kiki" are made up words. That is why you see quotes around the terms "correct" and "incorrect" to mean that you are using this term with reservations.
Volunteer Number of "Correct" Responses Number of "Incorrect" Responses Total Number of Responses
Table 1. In your lab notebook, make a data table like this one. You will be recording your results in this data table in your lab notebook.
  1. Find a volunteer. Tell them that you will show them a series of cards, and that you want to know if the picture is Bouba or Kiki but do NOT tell them what Bouba or Kiki mean.
    1. If they ask you for a definition, just explain that they are supposed to guess and do their best to decide.
  2. Show your volunteer the cards, one at a time.
  3. In the data table in your lab notebook, keep track of the number of "correct" and "incorrect" answers in the correct columns. There are 20 cards total, so the two numbers should add up to 20 when you are done with your volunteer, and you should write "20" in the "Total Number of Responses" column for each volunteer.
  4. Repeat steps 6 to 8 with at least four other volunteers, making a total of five volunteers.
    1. Try to ask as many volunteers as you can find to help you with your experiment. Be sure to collect data from each test subject.
  5. When you are finished, add up the total number of responses, the total number of "correct" responses, and the total number of "incorrect" responses for all volunteers. Write these numbers in the bottom row of your data table (the one labeled "Totals").
  6. Calculate the percentage of "correct" answers and the percentage of "incorrect" answers for all of your volunteers.
    1. To calculate the percentage of "correct" answers, divide the total number of "correct" responses by the total number of responses.
    2. To calculate the percentage of "incorrect" answers, divide the total number of "incorrect" responses by the total number of responses.
  7. Make a bar graph of your data to show whether more people were "correct" or "incorrect".
    1. On the x-axis (the horizontal axis going across), label one bar "correct" and label another bar "incorrect." On the y-axis (the vertical axis going up and down), put the percentage of each type of answer.
    2. You can make a graph by hand or use a website like Create a Graph to make a graph on the computer and print it.
  8. Did people usually give a "correct" answer, an "incorrect" answer, or was it about 50-50? What do you think your results mean?
icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.


  • Does the Bouba-Kiki Effect differ by age group? Ask each volunteer how old they are, and try to get volunteers from a series of age groups. What is the youngest group in which you can observe the Bouba-Kiki Effect?
  • Do you have an English as a Second Language (ESL) program at your school? Do you live near a cultural center where people speak other languages? Try the experiment on people who speak different languages, to see if it still works.
  • In this science project, you had the volunteers look at pictures you drew and identify them as Bouba or Kiki. Does it work the other way round? To try this experiment, give the volunteers a piece of paper and ask them to draw something that is Bouba or Kiki. Collect all of the drawings and score them for being pointy or rounded in shape.
  • What is it about the words "Bouba" and "Kiki" that make this work? Try an experiment swapping the vowel and consonant sounds, and see what happens for your experiment. Use the words "Bee-Bee" and "Kooka" instead of "Bouba" and "Kiki" when your volunteers are asked to look at the cards. If the results stay the same, then perhaps the consonant sounds of the "B" and the "K" are most important. If your results switch around, then the vowel sounds of the "ee" and the "oo" may be more important. What happens?


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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Science Buddies Staff. "The Bouba-Kiki Effect." Science Buddies, 20 Nov. 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/HumBeh_p026/human-behavior/bouba-kiki-effect?from=Blog. Accessed 24 Feb. 2024.

APA Style

Science Buddies Staff. (2020, November 20). The Bouba-Kiki Effect. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/HumBeh_p026/human-behavior/bouba-kiki-effect?from=Blog

Last edit date: 2020-11-20
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