A few years ago, two neuroscientists at the Massachusetts Institute of Technology (MIT) made a friendly bet on whether or not the human brain responded differently to harmonic tones (heard in music and speech) than our closest evolutionary relative, the macaque monkey. At the time, Bevil Conway and Sam Norman-Haignere worked in different MIT labs.

Back then, Conway's team at MIT was investigating possible differences between how monkeys and modern humans control vision; his lab's research unearthed very few differences in visual processing when comparing these species. At the same time, Norman-Haignere was researching auditory processing as a postdoctoral fellow in Josh McDermott's MIT Laboratory for Computational Audition, which studies how people hear.

Source: Courtesy of Conway lab, NIH

"I told Bevil [Conway] that we had a method for reliably identifying a region in the human brain that selectively responds to sounds with pitch," Norman-Haignere said in a statement. That's when Conway made a bet that if they compared humans and monkeys, they'd probably find very little difference between how primates and Homo sapiens respond to harmonic sounds with pitch. Spoiler alert: Conway eventually lost the bet.

In the video below, "Human Brain Prefers Pitch," Conway explains how this research unfolded and the significance of identifying that the human auditory cortex is more sensitive to pitch than the auditory cortex of Old World macaque monkeys.

"We found that a certain region of our brains has a stronger preference for sounds with pitch than macaque monkey brains," Bevil Conway said in a statement. "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."

Conway is currently an investigator in the NIH's Intramural Research Program and the senior author of a new paper, "Divergence in the Functional Organization of Human and Macaque Auditory Cortex Revealed by fMRI Responses to Harmonic Tones," published June 10 in Nature .

The first author of this paper, Sam Norman-Haignere (who won the above-mentioned bet), is currently a postdoc fellow at Columbia University's Zuckerman Institute for Mind, Brain, and Behavior. Josh McDermott, associate professor in the Brain and Cognitive Sciences department at MIT, is also a coauthor of this paper.

When the researchers first mapped the auditory cortex in human and monkey brains using fMRI neuroimaging, they didn't notice much difference between "hot spots" of activity relating to harmonic sounds with tone and toneless sounds. However, after doing a deeper dive into the data, Conway and colleagues unearthed evidence that the human auditory cortex is much more responsive to harmonic sounds with pitch than the monkey auditory cortex.

Norman-Haignere and his co-authors sum up their findings in the paper's abstract:

"We report a difference between humans and macaque monkeys in the functional organization of cortical regions implicated in pitch perception. Humans but not macaques showed regions with a strong preference for harmonic sounds compared to noise, measured with both synthetic tones and macaque vocalizations."

Two Sides of the Same Coin: Musical Harmony vs. Bellicose Vocalizations

As someone who grew up in a household with lots of very loud parental arguing, I blasted harmonic pop music on my headphones to block out the harsh vocal tones reverberating through the walls during mom and dad's ear-piercing verbal disagreements. This research offers fresh clues as to why so many of us are hypersensitive to specific vocal tones used during daily interactions and why a certain tone of voice (e. ., a mean boss barking orders) can instantly rub someone the wrong way.

For all of us who derive immense pleasure from hearing harmonic sounds and love listening to music, it's nice to have scientific evidence that helps to explain why modern humans of all generations are driven to create personalized soundtracks for our lives. It seems that music evolved as a universal part of our and that the human brain's auditory cortex is uniquely tuned for musical pitch. (See, "The Neuroscience of Hearing the Soundtracks of Your Life.")

In closing, the video below, "Mapping Musical Pitch in the Brain," elucidates the difference between harmonic tones (with pitch) and toneless noise.