What makes humans so unique? This question has persisted throughout the existence of mankind as we try to understand humanity and what sets us apart from our distant primate relatives, given that there are so many similarities. Recent research conducted by scientists from the Massachusetts Institute of Technology and the Laboratory of Sensorimotor Research, of the National Eye Institute of the National Institutes of Health, have shown that human brains have a bias for pitch. One way to look at this is that, in essence, music is a part of our evolution.
Researchers have found that humans and nonhuman primates process visual information the same way, yet the way they respond to different sounds was still unknown. The research team used functional MRI (FMRI) scans to compare and analyze how the brains of humans and rhesus macaques responded to auditory stimuli, in particular harmonic tones. In the paper, the authors wrote, “Speech and music contain harmonic frequency components, which are perceived to have ‘pitch’.” They found that humans had a strong response preference for pitch, though the same cannot be said for macaque monkeys. The monkey brains had about the same response to harmonic tones and noise.
The study featured four human participants and three rhesus macaques, for whom the researchers played harmonic tones and noise from five different frequency ranges. The initial analysis of the FMRI scans showed similar results, but upon closer inspection, they found that human brains appeared to be much more sensitive to pitch, compared to the macaque brains who did not seem to distinguish between harmonic tones and noise. Bevil Conway, PhD, senior author of the study notes, “These results suggest the macaque monkey may experience music and other sounds differently…In contrast, the macaque’s experience of the visual world is probably very similar to our own.”
Even though macaque calls have pitch and harmonic tones, when played to the rhesus macaques, the monkeys’ brains showed the same response. Conway writes, “[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.” He also poses a very interesting conclusion in regards to pitch and harmonic tones: “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.”
Language communication (speech) and music depend on pitch and are two aspects of human behavior that we often think of as being uniquely human. Dr. Conway’s study opens the floor for further research into the role of pitch (and subsequently, music) in human evolution. Where this study focuses on the responses of Old World monkeys, perhaps given proper funding, in the future the study can be extended to great apes that share more evolutionary similarities with humans, like chimpanzees and bonobos.