Visuoauditory mappings between high luminance and high pitch are shared by chimpanzees
(Pan troglodytes) and humans
Vera U. Ludwig, Ikuma Adachid, and Tetsuro Matsuzawa
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
Proceedings of the National Academy of Sciences of the United States of AmericaDEC/6/2011
see NATURE http://www.nature.com/news/the-chimpanzee-who-sees-sounds-1.9541
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