title: Visuoauditory mappings between high luminance and high pitch are shared by chimpanzees (Pan troglodytes) and humans.
abstract: 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.
authors.affiliation: Department of Psychiatry and Psychotherapy, Charité-Universitätsmedizin Berlin, D-10117 Berlin, Germany. vera.ludwig@charite.de
authors.forename: Vera U
authors.initials: VU
authors.lastname: Ludwig
authors.forename: Ikuma
authors.initials: I
authors.lastname: Adachi
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Matsuzawa
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D000818:Animals; D001307:Auditory Perception; D005260:Female; D006801:Humans; D007802:Language; D015233:Models, Statistical; D002679:Pan troglodytes; D010897:Pitch Discrimination; D013016:Sound; D013045:Species Specificity; D013997:Time Factors; D014785:Vision, Ocular; D014796:Visual Perception