Chimpanzee calls trigger a distinct response in the human brain

A small patch in the human auditory cortex responds more to chimpanzee calls than to other primate sounds. In 23 adults scanned in Geneva, that pattern stood out clearly.

The result points to shared vocal processing with great apes and hints at deep roots for voice recognition. It also suggests that what we call a voice system is tuned to specific acoustic cues.

What chimpanzee calls reveal

The work was led by Leonardo Ceravolo, research associate at the University of Geneva (UNIGE). His research focuses on how the brain encodes voices and social emotion.

The team identified a distinct response to chimpanzee calls in the anterior temporal voice areas during fMRI. 

“Our intention was to verify whether a subregion sensitive specifically to primate vocalizations existed,” said Ceravolo.

Participants listened to vocalizations from humans, chimpanzees, bonobos, and macaques. The team controlled for key acoustic features so the signal reflected species processing rather than simple pitch or loudness.

The brain data came from functional magnetic resonance imaging, a method that tracks blood flow as a stand-in for neural activity. 

The chimpanzee effect appeared in the anterior portions of the temporal cortex typically involved in voice perception.

How we process chimpanzee calls

Two decades ago, researchers mapped voice-preferring areas in the temporal cortex using fMRI. 

These temporal voice areas (TVA), clusters that prioritize voices over other sounds, help the brain decode identity and emotion. Monkeys also show a dedicated voice region in the auditory pathway. 

That comparative picture supports an older neural system for parsing species-specific calls.

In humans, different TVA pockets handle different jobs. Some focus on who is speaking, while others track emotional tone and social context.

Why bonobo calls differ

Bonobos produce calls with higher fundamental frequency, the basic pitch of a sound, than chimpanzees. This difference tracks shorter vocal folds in bonobos, a finding tied to their laryngeal anatomy.

If the TVA is tuned to voice-like pitches common to humans and chimps, bonobo calls may fall outside that sweet spot. That would match the present brain data without invoking species identity alone.

Acoustic proximity, not just evolutionary relatedness, seems to steer the human response. That is why chimp calls, closer to human pitch ranges, stirred the TVA more strongly than bonobo or macaque calls.

Early brain tuning

Even before birth, fetuses respond differently to their mother’s voice than to a stranger’s. Early sensitivity suggests voice pathways are primed well before speech.

Finding chimp sensitivity in adult TVA links that early tuning to older evolutionary circuitry. It hints at shared building blocks that language later builds upon.

These building blocks may include pitch ranges, timbre patterns, and timing features that overlap between human voices and chimp calls. The new work helps pinpoint where those overlaps land in the cortex.

How shared cues guide us

Chimpanzee calls carry emotional cues that map onto patterns humans understand automatically. These cues can include urgency, tension, or reassurance, and the auditory cortex picks them up even without training. 

The TVA response to these calls hints at a deeper set of social tools shaped long before language emerged.

Emotional decoding often depends on how fast the sound rises, its roughness, and its pitch patterns. 

These features appear in both human and chimpanzee communication. The overlap gives researchers a window into how early social groups may have relied on vocal cues to keep track of group members, danger, and cooperation.

Future research directions

“We already knew that certain areas of the animal brain reacted specifically to the voices of their fellow creatures. But here, we show that a region of the adult human brain, the anterior superior temporal gyrus, is also sensitive to non-human vocalizations,” said Ceravolo.

Future tests with gorilla or orangutan calls, and finer acoustic controls, could sharpen the map of which features drive TVA responses. 

That work would probe how social context and pitch combine in this anterior superior temporal gyrus, a sound-processing fold on the brain’s upper side.

The study narrows the gap between human speech systems and ancestral primate communication. It shows that our voice network is not a closed club and that certain ape calls still ring the bell.

The study is published in the journal eLife.

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