Ramachandran and Hubbard suggest that the kiki/bouba effect has implications for the evolution of language, because it 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.
Interestingly, individuals with autism do not show this effect. Where average people agree with the typical result 90% of the time, autistics only agree 60% of the time.
A similar experiment draws from feminine and masculine qualities that the human brain associates with numbers. Subjects were given two numbers: a 9 and an 11, and were asked which one seems feminine and which seems masculine. The majority of the subjects chose 9 as the one that portrayed feminine characteristics, but for unknown reasons.