Bouba/Kiki Effect

In 1929, German-American psychologist Wolfgang Köhler conducted groundbreaking psychological experiments on the Spanish-speaking island of Tenerife. 

Köhler showed participants forms similar to those shown above and asked which shape was called "takete" and which was called "baluba". 

Data suggested a strong preference to pair the jagged shape with "takete" and the rounded shape with "baluba".

In 2001, Vilayanur S. Ramachandran and Edward Hubbard repeated Köhler's experiment using the words "kiki" and "bouba" and asked American college undergraduates and Tamil speakers in India ,"Which of these shapes is bouba and which is kiki?" 

In both the English and the Tamil speakers, 95% to 98% selected the curvy shape as "bouba" and the jagged one as "kiki", suggesting that the human brain is somehow able to extract abstract properties from the shapes and sounds.

This suggests that the naming of objects is not completely arbitrary. The rounded shape may most commonly be named "bouba" because the mouth makes a more rounded shape to produce that sound while a more taut, angular mouth shape is needed to make the sound "kiki". The sounds of a K are harder and more forceful than those of a B, as well. 

The presence of these "synesthesia-like mappings" suggest that this effect might be the neurological basis for sound symbolism, in which sounds are non-arbitrarily mapped to objects and events in the world.