I too would associate "Bouba" with the rounded and "Kiki" with the sharper figure, but to me this is just a relatively universal sense of continuity vs discontinuities:<p>the local curvature is continuous for "Bouba", every point on the curve has a single tangent, which evolves continuously as you walk along this presented curve.<p>For Kiki: the local curvature is discontinuous: at the inward or outward points, there are 2 tangents, so the tangent abruptly switches value when passing through this point when walking along the curve.<p>similarly the "B"s in "Bouba" are <i>voiced</i> plosives, while the "K"s in "Kiki" are <i>unvoiced</i> plosives.<p>I think people would similarily classify "Titi, Pipi, Touta, Poupa, Kouka" like "Kiki" but "Didi, Douda, Bibi, Gigi, Gouga" like "Bouba".<p>The vowels are obviously voiced by the vocal chord <i>carrier wave</i> "voice".<p>So when we pass through the <i>unvoiced</i> (T/P/K) plosives, we notice discontinuity like the discontinuously evolving tangents along the boundary curve of the figure.<p>Obviously mammals like dogs have a concept of continuity, topology, distance, they might get spooked by "open" stairs, because they can see between the planks, etc.<p>And when we hear <i>voiced</i> (D,B,G) plosives, the voice while muted still evolves continuously.