If the brain of our ancestors was very similar to that of the monkey, it would have evolved to prefer speech and music to noise, unlike that of macaques, unable to tell the difference.
like the man, monkey is affected by midlife crisis. like the man, he plays politics, reasons and uses tools. And for good reason: its brain is very similar to that of humans. In 2012, a study thus proved that the brain of the bonobo and the common chimpanzee was same as 98.7% to ours. Last year, researchers even discovered that monkeys process visual information the same way we do. But what about auditory information?
According to a study published on June 10 in the journal Nature Neuroscience, although it has some similarities, the way in which the human brain and that of macaques receive sound differs slightly. Indeed, since the appearance of the first humans, our brain would have evolved to finally prefer music and speech to noise, unlike that of the monkey, unable to tell the difference.
To reach this conclusion, the researchers worked with three rhesus macaques and four humans. They had them listen to harmonic tones and noises with five different frequency ranges. Using MRI images, they measured brain responses. The first analysis shows no difference in brain responses between humans and monkeys: the same parts of the auditory cortices were activated in both species. On closer inspection, however, the researchers observed that human brains were far more sensitive to “spikes” in harmonic tones than animals, which did not seem to distinguish them from normal noise.
“The macaque monkey experiences music and other sounds differently”
However, these harmonic frequencies made of “peaks” or “pitches” are an integral part of speech and music, explains the study. And even when the researchers exposed the macaques to sounds with more natural harmonies (recordings of macaque calls), the results remained the same. Human brains are therefore more sensitive to “pitch”.
“We found that human and monkey brains had very similar responses to sounds in a given frequency range. It was when we added tonal structure to sounds that some of those same regions of the human brain became more responsive. “, notes Bevil Conway, lead author of the study. “We observed that a certain region of our brains had a stronger preference for sounds with pitch than the brain of monkeys (…) These results suggest that these sounds, which are part of music and speech , may have formed the basic organization of the human brain.”
In contrast, “these results suggest that the macaque monkey experiences music and other sounds differently.” “One wonders what kind of sounds our evolutionary ancestors experienced,” Conway wonders. Finally, this study may also “help explain why it has been so difficult for scientists to train monkeys to perform auditory tasks that humans find relatively easy,” he concludes.
A few years ago, a study on the brain of humans and monkeys had already highlighted the differences related to hearing. The researchers were thus able to observe that the ventrolateral prefrontal cortex is not linked in the same way to the brain areas involved in hearing in animals. “This explains why macaques do very poorly on some hearing tests. It also suggests that humans use what they hear to perform intellectual functions that macaques are unable to do,” noted the study.
