Key concepts
Human behavior

Do shapes have certain "sounds" to people, regardless of what language people speak? For example, does everyone associate certain physical characteristics, like sharpness and roundedness, with certain sounds? Understanding such similarities may not only help people better understand how languages develop, but it may also improve people's ability to communicate, especially when trying to cross language barriers. In this activity you'll investigate the "Bouba–Kiki effect" to find out how abstract shapes may be linked to sound.

One of the most amazing things humans do is use language to communicate. People have developed languages over many tens or hundreds of thousands of years, resulting in many very different tongues being spoken around the world today. How did our ability to use language evolve? Where and when was it first used?

One idea is that the first languages were representative sounds that people linked to concepts. Eventually these meaningful sounds grew more diverse and structurally intricate as they evolved into more complex speech. This idea brings with it a major question: Were the first sounds made by humans arbitrary and random, or were they consistently applied to certain symbols and concepts? A psychological phenomenon called the Bouba–Kiki effect has been used to help answer this question. In this effect, people are shown a pointy picture or a curvy, bubbly shape and asked to identify it as "Bouba" or "Kiki," even though those are both nonsense words. They are asked to do the same with a pointy, sharper shape. A surprising number of people identify the round shape as "Bouba" and the pointy shape as "Kiki" although they have not been told what the words mean. Will you observe the Bouba–Kiki effect or will you have the results of a 50–50 random-chance event?

•   A pen, pencil, or marker. You can use a colorful assortment if you want!
•   20 index cards
•   A piece of paper
•   At least five volunteers

•   On 10 index cards, draw a pointy, star-like shape, like the one shown in the illustration above.
•   On the other 10 index cards, draw round, bubbly shapes—like the one in the illustration above.
•   Randomly mix the cards by shuffling all of them together a few times.

•   Tell your first volunteer 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.
•   If they ask you for a definition, just explain that they are supposed to guess and do their best to decide.
•   Show your volunteer the cards, one at a time.
•   On a piece of paper keep track of the number of "correct" and "incorrect" answers. "Correct" answers are when the volunteer identifies a pointy, starlike shape with Kiki or a round, bubbly shape with Bouba. (Note that the answers your volunteers give you are not actually correct or incorrect, because "Bouba" and "Kiki" are made-up words.)
•   How many correct answers did the volunteer give? Did the volunteer give any incorrect ones, matching Kiki with the round shape or Bouba with the pointy shape?
•   Repeat these steps with at least five more volunteers. Use the same deck of index cards each time, but shuffle it so that the cards are randomly mixed.
•   When you finished, what was the total number of correct responses and the total number of incorrect responses from all volunteers? Did the volunteers mostly give correct responses?
•   Extra: Try to find volunteers from a series of different age groups and do this activity again. Does the Bouba–Kiki effect differ by age group? What is the youngest group in which you can observe the effect?
•   Extra: Give a new volunteer a piece of paper and ask the volunteer to draw something that is Bouba or Kiki. Try this with several new volunteers, collect all of the drawings, and score them for being pointy or rounded in shape. How well does this work? Does the volunteer always make a Bouba drawing rounded and a Kiki one pointy?
•   Extra: If you know people who speak different languages, try this activity on them. Does it still work?
•   Extra: What is it about the words "Bouba" and "Kiki" that make this work? Try this activity again but this time swap the vowel sounds by using the words "Bee-Bee" and "Kooka" instead of "Bouba" and "Kiki" when volunteers look at the drawings. Are the results the same, or do your results switch around? If they're the same, then perhaps the consonant sounds of the "B" and the "K" are most important, but if they're switched, then the vowel sounds of the "ee" and "oo" may be more important.

Observations and results
Did all of your volunteers identify the round shape as Bouba and the pointy shape as Kiki, even though they were not told what the words mean? Did you record no incorrect answers?

You most likely found that every volunteer you tested gave only correct answers, or almost entirely correct answers. In other words, the volunteers always, or nearly always, identified each round shape as Bouba and each pointy shape as Kiki. People who have different native languages make this association, as do even very young children most of the time. What does this mean? Is this evidence of a human predisposition to associating certain sounds with abstract concepts? This could indicate that humans did indeed apply the first sounds made in burgeoning languages to certain concepts or symbols, and that the associations with sounds in different languages are not actually random. One theory is that Bouba is associated with the round shape because a more rounded shape is made by our mouths when forming this sound whereas our mouths make a more angular shape when we say "Kiki." Additionally, "K" is a harder-sounding letter than "B." Those who use the modern Latin alphabet (including English speakers) may also be visually swayed: the written letters "K" and "B" are sharp and rounded, respectively.

More to explore
Jaron's World: The Meaning of Metaphor from Discover Magazine
Kiki Bouba: Play the Game from The Fat Duck, Ltd.
The shape of boubas: Sound–shape correspondences in toddlers and adults (pdf) from Daphne Maurer, Thanujeni Pathman, and Catherine J. Mondloch, Developmental Science
The Bouba–Kiki Effect from Science Buddies

This activity brought to you in partnership with Science Buddies