Visuoauditory mappings between high luminance and high pitch are shared by chimpanzees (Pan troglodytes) and humans.
Vera U. Ludwig, Ikuma Adachi, Tetsuro MatsuzawaDOI: 10.1073/pnas.1112605108
Humans share implicit preferences for certain cross-sensory combinations; for example, they consistently associate higher-pitched sounds with lighter colors, smaller size, and spikier shapes. In the condition of synesthesia, people may experience such cross-modal correspondences to a perceptual degree (e.g., literally seeing sounds). So far, no study has addressed the question whether nonhuman animals share cross-modal correspondences as well. To establish the evolutionary origins of cross-modal mappings, we tested whether chimpanzees (Pan troglodytes) also associate higher pitch with higher luminance. Thirty-three humans and six chimpanzees were required to classify black and white squares according to their color while hearing irrelevant background sounds that were either high-pitched or low-pitched. Both species performed better when the background sound was congruent (high-pitched for white, low-pitched for black) than when it was incongruent (low-pitched for white, high-pitched for black). An inherent tendency to pair high pitch with high luminance hence evolved before the human lineage split from that of chimpanzees. Rather than being a culturally learned or a linguistic phenomenon, this mapping constitutes a basic feature of the primate sensory system.
Ludwig VU. , Adachi I, Matsuzawa T(2011)Visuoauditory mappings between high luminance and high pitch are shared by chimpanzees (Pan troglodytes) and humans. Proc Natl Acad Sci U S A., published ahead of print December 5, 2011. https://dx.doi.org/10.1073/pnas.1112605108