What makes humans so different from other primates? Though our brains are similar, it seems
that they react differently to various stimuli. New evidence suggests that human brains "listen"
for musical pitch, a preference that scientists have not detected in monkeys.
Previous studies have shown that the brains of humans and nonhuman primates process visual
information in much the same way. Yet, researchers have remained unsure as to whether there
are any differences in how we and primates process different types of sounds.
In other words, while a gorilla can paint, can chimpanzee play drums?
This is precisely the area that scientists from the Massachusetts Institute of Technology in
Cambridge, MA, and the Laboratory of Sensorimotor Research, of the National Eye Institute of
the National Institutes of Health in Bethesda, MD, recently decided to investigate.
This is interesting, because the answer to both of those questions is yes, with the exact same
caveat: monkeys can produce art and music the way a computer can produce humor. It can
follow the forms, but it won't make anything.
In their study paper, which appears in Nature Neuroscience, the researchers explain that the
the visual cortex is similar between humans and macaque monkeys, but less is known about
audition" differences in the two species.
The research team thus set out to compare how the brains of humans and those of rhesus
macaques reacted to auditory stimuli, particularly ones that we usually associate with humans,
namely harmonic tones that characterize music and speech.
Speech and music contain harmonic frequency components, which are perceived to have
' pitch,'" the authors explain in their paper. Humans have cortical regions with a strong response
preference for harmonic tones versus noise, But is the same true for primates?
We found that a certain region of our brains has a stronger preference for sounds with pitch than
macaque monkey brains," says senior author Bevil Conway, Ph.D., commenting on the current
study's findings. The results raise the possibility that these sounds, which are embedded in
speech and music, may have shaped the basic organization of the human brain."
This would explain why monkeys like to play drums, but not flutes or trumpets.
For the study, the researchers worked with three rhesus macaques and four human participants,
playing them harmonic tones and noise that featured five different frequency ranges.
Using functional MRI images, the team measured the monkey and human brain responses to the
different sounds and frequency ranges.
The first analysis of functional MRI scans seemed to suggest that there was not much difference
in brain responses between humans and monkeys — both the human participants and the
macaques showed activation of the same parts of the auditory cortexes.
But when the researchers assessed the scans in more detail, they saw that human brains appeared
to be much more sensitive to "pitch" in harmonic tones than the brains of rhesus macaques,
which seemed not to distinguish between harmonic tones and regular noise.
We found that human and monkey brains had very similar responses to sounds in any given
frequency range. It's when we added tonal structure to the sounds that some of these same
regions of the human brain became more responsive," explains Conway.
This raises the question of why modern art has gone so far out of its way to producing music
without tunes and art without forms. Perhaps this is a question that answers itself, however, as
modern art seeks to pander to the widest possible audience, apparently including the animal
These results suggest the macaque monkey may experience music and other sounds differently,"
he continues, noting that, in contrast, the macaque's experience of the visual world is probably
very similar to our own."
Even when they exposed the macaques to sounds with more natural harmonies — namely,
recordings of macaque calls — the results remained the same, supporting the idea that human
brains are more sensitive to pitch.
The current findings may also help explain why it has been so hard for scientists to train
monkeys to perform auditory tasks that humans find relatively effortless," notes Conway.
At this point, it is worth noting that tone-deaf individuals, while they can’t sing, can still tell
whether or not a tune is being played on key. The same cannot be said for people who listen to
rap, reggae, and the rest of whatever they decide to ‘invent’ today (rock and roll not included.
Heavy metal fans are deaf, period).
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