What sets humans apart from other primates? New research suggests that one key difference may lie in how our brains process sound. While human and nonhuman primate brains respond similarly to visual information, humans appear uniquely tuned to musical pitch — a sensitivity not observed in monkeys.

A team of scientists from Massachusetts Institute of Technology (MIT) in Cambridge, MA, and the Laboratory of Sensorimotor Research at the National Eye Institute, NIH, investigated how human and macaque brains react to auditory stimuli. Specifically, they examined harmonic tones, the sound structures found in music and speech.

In their study, published in Nature Neuroscience, the researchers used functional MRI scans to monitor brain responses in four human participants and three rhesus macaques while exposing them to harmonic tones and noise across five frequency ranges.

Initial analyses suggested that both humans and monkeys activated similar areas in the auditory cortex. However, a deeper look revealed a critical difference: human brains are far more sensitive to pitch in harmonic tones, whereas macaque brains did not distinguish these tones from regular noise.

“Human brains show a stronger preference for sounds with pitch than macaque brains,” said senior author Bevil Conway, Ph.D. “This sensitivity may have shaped the organization of our auditory cortex and helps explain why humans create and appreciate music, whereas monkeys’ experiences of sound are fundamentally different.”

Even when macaques were exposed to natural vocalizations, the results remained the same, reinforcing the idea that our brains are uniquely attuned to harmonic structure. This sensitivity may also clarify why it is difficult to train monkeys in auditory tasks that humans perform effortlessly.

The study highlights that while monkeys may perceive the visual world similarly to humans, our auditory experiences — and by extension, our appreciation of music and speech — are distinct.