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Ludwig VU, Adachi I, Matsuzawa T.
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, doi: 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.
Vera U. LudwigPhD student, Department of Psychiatry and Psychotherapy, Charite - Universitatsmedizin Berlin
Ikuma AdachiAssistant Professor, Center for International Collaboration and Advanced Studies in Primatology (CICASP), Primate Reseach Institute, Kyoto University