Bouba/kiki effect

The bouba–kiki effect (/ˈbuːbə ˈkiːkiː/ BOO-bə KEE-kee) or takete–maluma phenomenon is a non-arbitrary mental association between certain speech sounds and certain visual shapes. The most typical research finding is that people, when presented with nonsense words, tend to associate certain ones (like bouba and maluma) with a rounded shape and other ones (like kiki and takete) with a spiky shape. Its discovery dates back to the 1920s, when psychologists documented experimental participants as connecting nonsense words to shapes in consistent ways.

There is a strong general tendency towards the effect worldwide; it has been robustly confirmed across a majority of cultures and languages in which it has been researched, for example including among English-speaking American university students, Tamil speakers in India, speakers of certain languages with no writing system, young children, infants, and (though to a much lesser degree) the congenitally blind. It has also been shown to occur with familiar names. The bouba–kiki effect is one form of sound symbolism.