I know that "Kiki" is angular: The metacognition underlying sound-shape correspondences.

We examined the ability of people to evaluate their confidence when making perceptual judgments concerning a classic crossmodal correspondence, the Bouba/Kiki effect: People typically match the "Bouba" sound to more rounded patterns and match the "Kiki" sound to more angular patterns instead. For each visual pattern, individual participants were more confident about their own matching judgments when they happened to fall in line with the consensual response regarding whether the pattern was rated as "Bouba" or "Kiki". Logit regression analyses demonstrated that participants' confidence ratings and matching judgments were predictable by similar regression functions. This implies that the consensus and confidence underlying the Bouba/Kiki effect are underpinned by a common process, whereby perceptual features in the patterns are extracted and then used to match the sound according to rules of crossmodal correspondences. Combining both matching and confidence measures potentially allows one to explore and quantify the strength of associations in human knowledge.