Before you open the spoiler below, I want you to think about the names "Kiki" and "Bouba."
Now look at the shapes in this image and decide which one is named Kiki and which one is named Bouba.
This was an experiment that was given to both American English speakers and Indian Tamil speakers. In both cases, 95-98% of participants called the image on the left "Kiki" and the image on the right "Bouba." The experiment shows that the human brain extracts abstract properties from images and sounds.
The creator of this experiment, V.S. Ramachandran, also said that this experiment shows evidence that everyone has synesthesia (connecting one sense to another, IE associating colors with sounds) to a certain degree, and this greatly contributed to the evolution of language. Cool, no?