NewScientist | They can't talk, but chimps may have some of what it takes to evolve language. That is the suggestion of a study which found chimps link sounds and levels of brightness, something akin to synaesthesia in people. Such an association could help explain how our early ancestors took the first vital step from ape-like grunts to a proper vocabulary.
Synaesthetes make unusual connections between different senses – they might sense certain tastes when they hear music, or "see" numbers as colours. This is less unusual than you might think: "The synaesthetic experience is a continuum," explains Roi Cohen Kadosh of University College London. "Most people have it at an implicit level, and some people have a stronger connection."
Now, Vera Ludwig from the Charite University of Medicine in Berlin, Germany, and colleagues have shown for the first time that chimpanzees also make cross-sensory associations, suggesting they evolved early on.
The team repeatedly flashed either black or white squares for 200 milliseconds at a time on screens in front of six chimpanzees (Pan troglodytes) and 33 humans. The subjects had to indicate whether the square was black or white by touching a button of the right colour. A high or low-pitched sound was randomly played in the background during each test.
Chimps and humans were better at identifying white squares when they heard a high-pitched sound, and more likely to correctly identify dark squares when played a low-pitched sound. But performance was poor when the sounds were swapped: humans were slower to identify a white square paired with a low-pitched noise, or a black square with a high-pitched noise, and the chimps' responses became significantly less accurate.
Synaesthetes make unusual connections between different senses – they might sense certain tastes when they hear music, or "see" numbers as colours. This is less unusual than you might think: "The synaesthetic experience is a continuum," explains Roi Cohen Kadosh of University College London. "Most people have it at an implicit level, and some people have a stronger connection."
Now, Vera Ludwig from the Charite University of Medicine in Berlin, Germany, and colleagues have shown for the first time that chimpanzees also make cross-sensory associations, suggesting they evolved early on.
The team repeatedly flashed either black or white squares for 200 milliseconds at a time on screens in front of six chimpanzees (Pan troglodytes) and 33 humans. The subjects had to indicate whether the square was black or white by touching a button of the right colour. A high or low-pitched sound was randomly played in the background during each test.
Chimps and humans were better at identifying white squares when they heard a high-pitched sound, and more likely to correctly identify dark squares when played a low-pitched sound. But performance was poor when the sounds were swapped: humans were slower to identify a white square paired with a low-pitched noise, or a black square with a high-pitched noise, and the chimps' responses became significantly less accurate.
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